The other translations use “tree” (NASB [footnotes it could also be “cross”], ESV, CSB, NRSV, NET, NLT, KJV). Of course, Jesus never hung on a tree. The cross was made from wood, but it wasn’t a tree. Saying he was “hung” creates an image for a modern person that isn’t accurate; there was no noose.
Paul is referring to Deut 21:23: “you must not leave the body hanging on the pole overnight. Be sure to bury it that same day, because anyone who is hung on a pole is under God’s curse” (NIV) The Hebrew עֵץ is defined by HALOT as “tree” or “timber” and all translations use “tree” except for the NIV. But executed criminals were generally impaled on a pole, which explains the NIV translation.
This illustrates how difficult it can be to connect a NT passage to its OT allusion, and how the specifics of the ancient OT culture can make the translation even more difficult. By using “pole,” the NIV is uniquely calling attention to the fact that Jesus was not hung on a tree as in the wild west, but that his body was displayed for all to see on a pole, a pole in the shape of a cross made of wood.
The translation of a person hung on a tree creates an incorrect image of the crucifixion. Hung on a pole is not much better, but how else can you say Jesus’ body was displayed on something made of wood in a way that reflected ancient practice and fulfillment of Deut 21:23?
