The second commandment forbids the use of any physical representation of something used in the worship of God. It prohibits anything that tries to represent divinity in a physical way, such as pictures or statues. The crucifix (an image of Jesus on the cross) certainly fits into this category. Even though the stated intent is for use as a remembrance of the crucifixion, God commands us not to use any image or likeness in our worship of Him.
The cross has been used as a religious symbol since long before the crucifixion of Jesus. It originated in the Babylonian mystery religions, where it was a symbol of the god, Tammuz. In his book The Two Babylons, Alexander Hislop summarizes the universality of the cross by saying that “there is hardly a pagan tribe where the cross has not been found.” The cross did not even become associated with nominal Christianity until the time of Constantine, centuries after the crucifixion. And while the Scriptures refer to the cross metaphorically, the apostolic church never made use of it in a physical way.
In addition to the pagan origin, the question is still unresolved exactly what Jesus died on. The Greek word translated as “cross” is stauros, meaning a stake or upright pole. It may have had a cross-beam on it, or it may have simply been a long piece of wood, thick enough to bear the weight of a human body. Adding to the mystery are four scriptures asserting that Jesus was hung on atree (Acts 5:30; 10:39; 13:29; I Peter 2:24), and the Greek indicates a green, living tree rather than a stauros of dead wood. Because of this, one possibility is that the stauros of Jesus was just the crossbeam, which was attached to a living tree.
But the traditions of nominal Christianity have memorialized the pagan cross. To add insult to injury, millions venerate the means of death of the Messiah through their physical representations, rather than commemorating His death as He commanded, through the annual observance of the Passover (see I Corinthians 11:24-25). Hebrews 12:2 says that Jesus Christ despised the shame of the cross in order to become our Savior, yet nominal Christianity both memorializes that shame in an image and turns it into a good-luck charm.
In studying Christ's instructions for taking up or bearing our stauros, it is clear that He did not intend for us to have anything to do with a physical crucifix, any more than He intended for us literally to pluck out an eye or cut off a hand to avoid sin (see Matthew 5:29-30). Rather, the use of the cross stands for a much larger concept that cannot—and should not—be crammed into a mere icon.
The Jews living under Roman dominion were all too familiar with crucifixions. When they saw a man carrying a stauros, it could only mean that his time on earth was essentially finished; they knew that man was as good as dead. So when Jesus told His followers to take up their crosses, they also were to account themselves as already being dead. What life remained was given over to the control of another, symbolizing complete surrender, while pointing to the encumbered life of a disciple.
David C. Grabbe
What Does It Mean to Take Up the Cross?