In his letter to the Galatians, he stresses that it was specifically a death by crucifixion that mattered for salvation. If Jesus had been stoned to death, for example, or strangled, that would have been one thing. But because he was crucified, in particular, he was able to bear the “curse” of sin that other people deserved. And that is because the scriptures indicate that anyone who “hangs on a tree” is cursed by God (Gal. 3:10–13). This is a reference to the law of Moses, Deuteronomy 21:23, which states: “cursed is everyone who hangs on a tree.”
