In Luther’s Small Catechism, he says that every Christian should make the sign of the cross in the morning and evening before praying:

In the morning, when you rise, you shall bless yourself with the holy cross and say:
In the name of God the Father, Son, and Holy Ghost. Amen.

In the evening, when you go to bed, you shall bless yourself with the holy cross and say:
In the name of God the Father, Son, and Holy Ghost. Amen.

Small Catechism, Daily Prayers, 1, 4

And since then, Lutherans have been doing exactly that. But from where does this practice come? Is it just a holdover from the medieval church? In this post, I demonstrate the grounds for this practice and contend that it is very likely apostolic in origin, but if not, it is at least from the apostolic age. If you’re solely interested in the explicit evidence, skip to the section about the earliest witnesses as the Scriptural foundations section is more about the grounds for the practice.

Scriptural foundations

Old Testament precursors

The sign of the cross is not explicitly mentioned anywhere in scripture (though neither is folding one’s hands or closing one’s eyes in prayer), but many foundations are laid for it both in scripture and, more abstractly, pre-incarnation extra-Biblical sources (as discussed later). Physical signs marking Israel as saved by Christ and imprinted with His Spirit are precursors of this Christian practice, and in the New Testament, the language surrounding this spiritual reality lend themselves well to Christians making a habit of remembering this in a physical way.

Beginning in plagues in Egypt, Israel marked itself with a sign to separate itself from pagan Egyptians. Exodus 12:23: “For the Lord will pass through to strike the Egyptians; and when He sees the blood on the lintel and on the two doorposts, the Lord will pass over the door and not allow the destroyer to come into your houses to strike you.” This mark on their doors was the blood of the first Passover lamb, a prefigurement of Christ crucified. Marked with this blood, judgment was not dealt to them.

Later in Exodus, Aaron and the high priests after him are given a sign to wear on their foreheads. Exodus 28:38: “You shall also make a plate of pure gold and engrave on it, like the engraving of a signet: HOLINESS TO THE LORD. And you shall put it on a blue cord, that it may be on the turban; it shall be on the front of the turban. So it shall be on Aaron’s forehead, that Aaron may bear the iniquity of the holy things which the children of Israel hallow in all their holy gifts; and it shall always be on his forehead, that they may be accepted before the Lord.” And this practice was also held among Israelites. Deuteronomy 6:6-8: “And these words which I command you today shall be in your heart. You shall teach them diligently to your children, and shall talk of them when you sit in your house, when you walk by the way, when you lie down, and when you rise up. You shall bind them as a sign on your hand, and they shall be as frontlets between your eyes.” Deuteronomy 18:11: “Therefore you shall lay up these words of mine in your heart and in your soul, and bind them as a sign on your hand, and they shall be as frontlets between your eyes.” And this practice has allusions in Exodus 13:9-16. The practice continued into the time of the New Testament (Matthew 23:5). These phylacteries were to remind Israel of God’s salvation and were specifically for remembrance on certain occasions, which Christians have maintained. This is why we cross ourselves when we wake up, go to sleep, sit in our house to eat, or travel (praying the Itinerarium). Particularly important to note is that these phylacteries resided on the forehead, which is where early Christians crossed themselves, and to this day is still a place of crossing in certain Christian rites such as application of chrism in chrismation, imposition of ashes on Ash Wednesday, and during the announcement of the Gospel reading in the mass.

In the end of the Old Testament, God commanded Ezekiel to place a mark on the foreheads of Israelites mourning over abominations in the Temple. Ezekiel 9:3-4: “Now the glory of the God of Israel had gone up from the cherub, where it had been, to the threshold of the temple. And He called to the man clothed with linen, who had the writer’s inkhorn at his side; and the Lord said to him, ‘Go through the midst of the city, through the midst of Jerusalem, and put a mark (Hebrew: tāv) on the foreheads of the men who sigh and cry over all the abominations that are done within it.'” The tāv is the last letter in the Hebrew alphabet and in paleo-Hebrew, which would have been in use at the time, resembled a cross. Origen’s (185-253 AD) commentary on this (and other church figures after him follow suit) explains, “A third, one of those who have come to faith in Christ, said that in the old-style [paleo-Hebrew] letters, Tau [this is the Greek character t, which corresponds to the Hebrew tāv here] resembles the form of the cross, and that there is a prophecy here concerning the sign placed on the foreheads of Christians—which all believers make when beginning any activity at all, especially prayer or holy readings.” This connection is fairly direct; these Israelites had a mark, in the shape of a cross, place on their foreheads, which is what we Christians do today.

New Testament spiritual foundations

In the New Testament, a number of passages point toward spiritual realities, upon which the sign of the cross is based.

In Mark 8:34 Jesus says, “Whoever desires to come after Me, let him deny himself, and take up his cross, and follow Me.” The sign of the cross is to remind ourselves that we are to take up our cross daily. Just as the cross was placed on Jesus, so we have the sign of the cross placed on us.

Paul says in Romans 13:14, “[P]ut on the Lord Jesus Christ,” and the sign of the cross is a representation of this. We place the cross on ourselves, and the cross represents the work of Christ.

2 Corinthians 1:21-22: “Now He who establishes us with you in Christ and has anointed us is God, who also has sealed us and given us the Spirit in our hearts as a guarantee.” The sign of the cross is a symbol of the seal placed upon us. In particular, this is reflected in the chrismation rite, in which we are anointed with oil in the sign of the cross, including the forehead, as mentioned earlier, but also upon the heart, reflecting that the Spirit is in our hearts and sealed there as Paul says again in Ephesians 1:13, “you were sealed with the Holy Spirit of promise.”

Galatians 2:20: “I have been crucified with Christ; it is no longer I who live, but Christ lives in me; and the life which I now live in the flesh I live by faith in the Son of God, who loved me and gave Himself for me.” The sign of the cross represents that we have been crucified with Christ, placing the cross onto ourselves.

Galatians 6:17: “From now on let no one trouble me, for I bear in my body the marks of the Lord Jesus.” The sign of the cross marks our bodies with the marks placed on Jesus in His crucifixion.

Revelation 7:1-4: “After these things I saw four angels standing at the four corners of the earth, holding the four winds of the earth, that the wind should not blow on the earth, on the sea, or on any tree. Then I saw another angel ascending from the east, having the seal of the living God. And he cried with a loud voice to the four angels to whom it was granted to harm the earth and the sea, saying, ‘Do not harm the earth, the sea, or the trees till we have sealed the servants of our God on their foreheads.’ And I heard the number of those who were sealed. One hundred and forty-four thousand of all the tribes of the children of Israel were sealed.” And 9:4: “They were commanded not to harm the grass of the earth, or any green thing, or any tree, but only those men who do not have the seal of God on their foreheads.” And 14:1 “Then I looked, and behold, a Lamb standing on Mount Zion, and with Him one hundred and forty-four thousand, having His Father’s name written on their foreheads.” In these three passages, Christians are marked with a sign on their forehead, specifically the name of the Father, YHWH. Again, like in the Old Testament passages, a visible sign is placed on the forehead to indicate salvation, and we imitate this by making the visible sign of the cross on ourselves, including on the forehead. Bede (673-735 AD) comments on Revelation 7:3: “Hurt not: From the time that the Lord suffered, not only was the dominion of the enemy who opposed Him destroyed, but that of worldly power too, as we both see with our eyes… [that is, on our] foreheads. For to this end was the empire of the nations broken up, that the face of the saints might be freely marked with the seal of faith, which these had resisted. For, again, the figure of the cross itself represents the kingdom of the Lord extending everywhere, as the old saying proves: ‘Behold the world four-square, in parts distinct, To shew the realm of faith possessing all.’ And not in vain was the sacred Name of the Lord, of four letters, written on the forehead of the High Priest, inasmuch as this is the sign on the forehead of the faithful, of which it is also sung in the Psalm [8:1]: ‘O Lord, our Lord, How excellent is Your name in all the earth.'” And this idea of the cross being stretched across the world in four directions is a theme in early Christianity which is related to the practice of signing the cross, to be discussed next.

The earliest witnesses

Related ideas building on sources before the 2nd century AD

Before getting to the earliest explicit witnesses, I think it’s worth mentioning some early ideas related to this practice going back to Plato and the appropriation of Plato by early Christians. In Plato’s Timaeus, he describes the creation of the world and in 34a-36b, the soul of the world, which is a divine thing of sorts, is stretched across the body of the world in the shape of a cross. This tradition was inherited from earlier Pythagoreans (Pythagoras lived 570-495 BC) who likely got it from the ancient near east. Justin Martyr (100-165 AD) in his First Apology 55 takes Plato’s tradition about the world soul to be about the Logos (Greek for “Word”), a common identification in the Middle-Platonists, including Philo of Alexandria (20 BC-50 AD), the Jewish Platonist. Philo also connects the Logos to the Angel of the Lord in the Old Testament, which Christians have identified with the pre-incarnate Christ (similarly the Word and Name of the Lord in the Old Testament). This Logos is identified with Jesus in the first chapter of the Gospel of John. Putting these things together, Justin takes the stretching out of the world soul, IE the Logos, in the shape of a cross onto the body of the world to be about Christ being impressed upon creation in cruciform shape. Justin Martyr does not make this next step, but it is fitting: Man, as a microcosm of creation, then puts impresses upon himself the shape of the cross in this ritual.

Irenaeus (130-202 AD) makes the same connection in Demonstration of the Apostolic Preaching 34: “Now seeing that He is the Word of God Almighty, who in unseen wise in our midst is universally extended in all the world, and encompasses its length and breadth and height and depth— for by the Word of God the whole universe is ordered and disposed—in it is crucified the Son of God, inscribed crosswise upon it all: for it is right that He being made visible, should set upon all things visible the sharing of His cross, that He might show His operation on visible things through a visible form. For He it is who illuminates the height, that is the heavens; and encompasses the deep which is beneath the earth; and stretches and spreads out the length from east to west; and steers across the breadth of north and south; summoning all that are scattered in every quarter to the knowledge of the Father.”

Earliest explicit witnesses

Now that foundations and precursors have been covered, we can move onto the earliest explicit witnesses.

The earliest extant source to mention the sign of the cross explicitly is the Acts of Paul and Thecla. This work was written between 95 and 200 AD, but is likely from the early 2nd century in my estimation, as Dunn has argued (more thoroughly than any other source I have seen). For evidence on this, see his PhD Dissertation and further comments of his in this blog post. In reply to the original edition of this blog post (IE the one you are reading, not his post previously linked), he made comments on Facebook, which I will here quote:

Thanks for mentioning and linking my PhD dissertation. For what it is worth, I now argue that the Acts of Paul should date in the early second century based on several criteria: (1) form of persecution; (2) orthodoxy displayed; (3) heresies encountered; (4) evident ignorance of NT texts, esp. Acts.

I’ve yet to publish anything on why I think the AP represents earlier persecution. The suggestion that Christians should die for the name of Christian would be post-Trajan’s rescript (to Pliny, AD 111-113), and yet no one actually dies for that even though it is suggested by Demas and Hermogenes to Thamyris. So evidently, we are still in the early second century when martyrs died for their impious, evil deeds, rather than just for carrying the name Christian. I thus conclude that the conditions of persecution suggest pre-Trajan’s Rescript. Contrast the later 2nd century martyrdoms in the Acts of Christian Martyrs, Musurillo.

Peter Dunn, two Facebook comments in Patristics for Protestants on January 22, 2024

The text purports to record events that occurred during the life of Paul, who is himself mentioned (alive) immediately before the part about making the sign of the cross. Paul died in 64/65 AD. If the event described in this quote is true, then the practice is certainly apostolic, if the event described is not, it still provides compelling evidence for an apostolic or near-apostolic origin of the practice. If the author, living in the early 2nd century, included the detail about making the sign of the cross while this was yet a novel practice, his audience would have immediately called out the historical anachronism (we have no evidence that this occurred, despite only slightly later sources critiquing the document). Unless the author was a fool, he would not intentionally include an historical anachronism. This makes it likely that the practice at least pre-dated living memory in the early 2nd century, being at least a lifetime earlier in origin, for then nobody could immediately point out the anachronism of a practice that developed in the audience’s own lifetime without drawing on older testimonies. It’s also worth mentioning that the author does not explain the practice at all, which suggests the intended audience would be familiar with the practice already, meaning it was likely widespread by this time. This places the practice firmly in the apostolic age.

Now the boys and the maidens brought wood and hay to burn Thecla: and when she was brought in naked, the governor wept and marvelled at the power that was in her. And they laid the wood, and the executioner bade her mount upon the pyre: and she, making the sign of the cross, went up upon the wood. 

Acts of Paul and Thecla 22

The next earliest source on the sign of the cross is Tertullian (155-220 AD). He is speaking of what he believes to be ancient customs that are widespread in his time, which ends with making the sign of the cross on the forehead, so by the early 3rd century, this practice was widespread certainly, and not only that, but Tertullian claims this practice is ancient custom that demands our submission.

And how long shall we draw the saw to and fro through this line, when we have an ancient practice, which by anticipation has made for us the state, i.e., of the question? If no passage of Scripture has prescribed it, assuredly custom, which without doubt flowed from tradition, has confirmed it. For how can anything come into use, if it has not first been handed down? Even in pleading tradition, written authority, you say, must be demanded. Let us inquire, therefore, whether tradition, unless it be written, should not be admitted. Certainly we shall say that it ought not to be admitted, if no cases of other practices which, without any written instrument, we maintain on the ground of tradition alone, and the countenance thereafter of custom, affords us any precedent. To deal with this matter briefly… At every forward step and movement, at every going in and out, when we put on our clothes and shoes, when we bathe, when we sit at table, when we light the lamps, on couch, on seat, in all the ordinary actions of daily life, we trace upon the forehead the sign.

If, for these and other such rules, you insist upon having positive Scripture injunction, you will find none. Tradition will be held forth to you as the originator of them, custom as their strengthener, and faith as their observer. That reason will support tradition, and custom, and faith, you will either yourself perceive, or learn from some one who has. Meanwhile you will believe that there is some reason to which submission is due.

Tertullian, The Chaplet 3-4

Hippolytus (170-235 AD) describes the rites for baptism and chrismation, which immediately follows, in his work The Apostolic Tradition, and this rite includes making the sign of the cross on the forehead with chrism, as is still done to this day. Notably, this work purports to be describing traditions passed from the apostles themselves, which is yet another argument for this practice being apostolic in origin, but even if it is slightly later (for it is at the latest from the end of the first century), this document further adds to such evidence since it could not purport to be apostolic practice if it weren’t at least from before the living memory of the audience.

Then the bishop, laying his hand upon them, shall pray, saying, “O Lord God, who hast made them worthy to obtain remission of sins through the laver of regeneration of [the] Holy Spirit, send into them thy grace, that they may serve thee according to thy will; for thine is the glory, to the Father and the Son, with [the] Holy Spirit in the holy church, both now and world without end. Amen.” Then, pouring the oil of thanksgiving from his hand and putting it on his forehead, he shall say, “I anoint thee with holy oil in the Lord, the Father Almighty and Christ Jesus and [the] Holy Ghost.” And signing them on the forehead he shall say, “The Lord be with thee;” and he who is signed shall say, “And with thy spirit.” And so he shall do to each one. And immediately thereafter they shall join in prayer with all the people, but they shall not pray with the faithful until all these things are completed. And at the close of their prayer they shall give the kiss of peace.

Hippolytus, The Apostolic Tradition 22

Conclusion

I believe the evidence from the earliest sources leads us to the conclusion that this practice is indeed apostolic. We have an explicit source from almost immediately after the time of the apostles claiming that it is apostolic, and two from a generation or two later that claim the same. We have no reason to believe all three sources are fabricating evidence or merely mistaken, especially given that Hippolytus has always been regarded by the church as a saint, and he was bishop of Rome, the highest seat in all of Christendom. The evidence firmly supports a first century date, even if one finds it unconvincing that the practice is apostolic in origin. Numerous scriptural texts and even pre-New Testament sources prefigure the practice and lay grounds for it, showing why the practice arose and spread so early and so quickly.