Crucifixion

The first mention of crucifixion (obtaining life through the tree), not merely death is Genesis 1:12:

Ge 1:11 And God said, Let the earth bring forth grass, the herb yielding seed, [and] the fruit tree yielding fruit after his kind, whose seed [is] in itself, upon the earth: and it was so. {grass: Heb. tender grass}

The tree is a reference to the cross. It is through Christ's death and resurrection that he bore fruit, and his fruit was vital, having life (seed) of it's own.

Notice that 'tree' is singular. There is only one cross, but many literal trees. Had God intended to speak of literal trees, a plural העצים trees would have been used rather than the singular עץ. There are many places where the singular is 'curiously' used.

The word עץ tree means (h. flesh with holiness and grace put to death)