Paul said, “But far be it from me to glory except in the cross of our Lord Jesus Christ, by which the world has been crucified to me, and I to the world” (Gal 6:14).

“The Sign of the Cross is indeed a distinctly Catholic (and Orthodox) practice, but it is also one that is deeply rooted in both the Old and New Testaments. Its witness to a faith that is ever ancient, yet ever new is yet another way the Sign of the Cross symbolizes the heart of what we believe and practice as Catholics.” -Excerpts from Scott Hahn’s book, “Signs of Life“.

Many Protestants have heard that the sign of the cross was “invented” by the Catholic church in 300 A.D. That misconception comes from a book called “Roman Catholicism” by Lorraine Boettner. In the book, he lists what he calls”Some Roman Catholic Heresies and Inventions. Many of the “inventions” on his list are fabricated as I pointed out in “Did the Catholic Church Ban, Burn or Chain bibles to Keep Laymen from Reading the Bible”? Here is what he says about making the sign of the cross, apparently hoping to imply that the practice was “invented” inn 300 A.D:

Item: “Making the sign of the cross . . . [A.D.] 300.”

“That’s it. That’s the whole charge: that the sign of the cross was not “invented” until well into the Christian era. In reality, we can show that Christians were making the sign of the cross at a much earlier date. The theologian Tertullian, writing in A.D. 211, said that “In all our travels and movements in all our coming in and going out, in putting of our shoes, at the bath, at the table, in lighting our candles, in lying down, in sitting down, whatever employment occupieth us, we [Christians] mark our foreheads with the sign [of the cross]” (The Chaplet [Crown] 3). Making the sign of the cross was already an old custom when he wrote. It may well have been common even while the apostles were alive”.

-Catholic Answers More Catholic “Inventions

Scott Hahn, in “Signs of Life” expounds, “We could fill a book with the early Christians’ testimonies to this practice. It was their favorite devotion as it required no special knowledge or skill. You didn’t have to be literate to make the Sign of the Cross, or rich enough to own a book of instructions. All you needed was one working finger. Martyrs made the Sign as they were taken to their death. Even Julian, the notoriously ex-Christian emperor, fell back to tracing the Sign whenever he felt oppressed by demons.

“It’s no small thing we do when we make the Sign of the Cross. It should take our breath away—but only so that we can be filled up with another wind, another breath: the Spirit of God.

This is the life we received in baptism, when we were marked with the Sign and saved from our sins. The early Christians compared this to the mark on the brow of Cain (Gen 4:15), which protected him from the punishment he deserved. They saw it foreshadowed also in the mark of blood on the doorposts that saved the firstborn sons of the Israelites at the Passover (Ex 12:7). They saw it even more vividly depicted in the oracle of the prophet Ezekiel, who saw that the righteous in Jerusalem would one day be saved because of a “mark upon the foreheads” (Ez 9:4). What was that mark? According to the ancient rabbis, it was tav, the last letter of the Hebrew alphabet, which in ancient times was drawn as a cross. In the New Testament, in the book of Revelation, St. John saw the faithful in heaven distinguished by this Sign on their foreheads (Rev 14:1, 22:4). “Signs Of Life”, Scott Hahn (emphasis mine)

The Catechism of the Catholic Church tells us that when Catholics are baptized “the sign of the cross, on the threshold of the celebration, marks with the imprint of Christ the one who is going to belong to him and signifies the grace of the Redemption Christ won for us by his cross” (CCC 1235).

Thereafter, each time we make the sign of the cross we remember that we belong to Christ. –“What is the Significance of Making the Sign of the Cross Before and After Private Prayer”? Catholic Answers

This short video answers 3 questions about the sign of the cross: What does it mean? What is your price tag? Why did God make you?