The Cross was given to us as a sign on our forehead, just as the circumcision was given to Israel:
for by it we believers are separated and distinguished from unbelievers.
This is the shield and weapon against, and trophy over, the devil. This is the seal that the destroyer may not touch you (Ex. 12:23), as says the Scripture…
The tree of life which was planted by God in Paradise prefigured this precious Cross.
For since death was by a tree, it was fitting that life and resurrection should be bestowed by a tree. St. John of Damascus