The cross has become the central symbol of Christianity, but why do some insist Jesus was crucified on a pole or a stake? Are there any clues in the Bible and historical records?
Let me begin by saying that the shape of the cross of Christ does not change the Bible holds about His death and resurrection. Almost all historians consider the crucifixion of Jesus a historical fact. The Romans exercised a lot of creativity with public execution, using gruesome and humiliating methods to enforce the rule of law. Though crucifixion often meant the condemned would carry their cross beam to the location where they were nailed or lashed to it and then placed on the upright post, live trees, walls, simple upright poles, and X-shaped crosses were all employed in the empire at one time or another. Josephus and Seneca the Younger confirm that many of methods were used in Jerusalem.
You might note that you see the word “cross” clearly in your English translation. The Greek word used for cross is “stauros” which was used by pre-Roman Empire Greek writers to describe poles or stakes used for fencing. Early Christian writers, including Justin Martyr, writing just after the time of the writing of the New Testament describe the cross in the shape of the capital T, sometimes with a small upright above the arms.
Though the Bible doesn’t describe the shape of the cross, there are two small clues in the book of John. Thomas, skeptical after not being present when the resurrected Jesus appeared to the other apostles, announces, “unless I see the nail marks in his hands and put my finger where the nails were, and put my hand into his side, I will not believe.” Thomas refers here to “nails” plural, speaking only of Jesus’ hands and the spear wound in His side. Were Jesus to be crucified on a pole, there would have been only one nail used for His hands. Two nails used in His hands would suggest a cross.
Tradition holds that Peter was crucified, requesting an upside down cross out of humility. During the restoration of Peter in John 21, Jesus speaks metaphorically about Peter’s future martyrdom: "When you are old you will stretch out your hands, and someone else will dress you and lead you where you do not want to go.” Given the two traditional sources of Peter’s crucifixion, it’s very likely that Jesus used “stretch out your hands” to refer to a crucifixion via a cross with a crosspiece.
Those two clues may be ample evidence to some or idle speculation to others. There’s not enough description in the Bible to make a dogmatic statement. Those that do insist on a particular type of cross may also package it with other agendas, trying to discredit the deity of Jesus or the truth of His resurrection.