The Sign of the Cross by Winkipedia (Latin: Signum Crucis) is a ritual hand motion made by members of most but not all branches of Christianity. It may be accompanied by the trinitarian formula. For Christians the motion symbolizes the Cross on Calvary by tracing the shape of the cross in the air or on one's own body.
The practice of tracing the sign of the cross is most prominent in the Roman Catholic church but is also practiced among the Eastern Orthodox and Episcopalians.
The history of the sign of the cross goes back as far as Tertullian, the early church father who lived between 160 and 220 A.D. Tertullian wrote, "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 mark our foreheads with the sign of the cross."
Huh! What a weird doctrine.
Catholics find support for the sign of the cross primarily in their many years of church tradition and, secondarily in Ezekiel 3:8; 9:4 and Revelation 7:3; 9:4; 13:16; 14:1.
While the passages do speak of a sign on the forehead for protection from God's judgment, there is no reason to believe that any of the verses prescribe the ritualistic sign of the cross.
The sign was soon recognized as a powerful protection against demonic forces, especially through its dramatic effect in exorcism for it causes the demons to tremble in fear.
Note that in the following verses, the presence of God the father or Jesus Christ does not make the demons to fear or disappear.
Job 1:6 Now there was a day when the sons of God came to present themselves before the LORD, and Satan came also among them.
Job 1:7 And the LORD said unto Satan, Whence comest thou? Then Satan answered the LORD, and said, From going to and fro in the earth, and from walking up and down in it.
Also, the presence of Jesus in this verses don't automatically cast demons out until Jesus said unto them to go.
Matthew 8:31 So the devils besought him, saying, If thou cast us out, suffer us to go away into the herd of swine.
Matthew 8:32 And he said unto them, Go. And when they were come out, they went into the herd of swine: and, behold, the whole herd of swine ran violently down a steep place into the sea, and perished in the waters.
What cast out demons is the word of God.
Hebrews 4:12 For the word of God is quick, and powerful, and sharper than any twoedged sword, piercing even to the dividing asunder of soul and spirit, and of the joints and marrow, and is a discerner of the thoughts and intents of the heart.
For us Christians, submitting ourselves to God by obeying His commandments is the only way to let the devils out.
James 4:7 Submit yourselves therefore to God. Resist the devil, and he will flee from you.
This mystical aspect of the sign of the cross, as some believers perceived, is completely false and cannot be supported by any verses in the Bible in any way.
If it symbolizes something that is not written, can not be read & therefore not biblical, then, don't do it for your goodness sake.