John Chrysostom

Seest thou the cause of the Crucifixion, and the salvation which is by it? Seest thou the relationship of the type to the reality? there the Jews escaped death, but the temporal, here believers the eternal; there the hanging serpent healed the bites of serpents, here the Crucified Jesus cured the wounds inflicted by the spiritual dragon; there he who looked with his bodily eyes was healed, here he who beholds with the eyes of his understanding put off all his sins; there that which hung was brass fashioned into the likeness of a …

Homily on the Gospel of John 27 ↗

Thomas Aquinas

Now the fruit of Christ's passion is eternal life; hence he says, so that everyone who believes in him, performing good works, may not be lost, but have eternal life. And this fruit corresponds to the fruit of the symbolic serpent. For whoever looked upon the serpent of bronze was freed from poison and his life was preserved. But he who looks upon the lifted up Son of Man, and believes in the crucified Christ, he is freed from poison and sin: "Whoever believes in me will never die" (below 11:26), and is preserved for eternal life. …

Commentary on John ↗

Bonaventure

"That everyone who believes in Him may not perish, but may have eternal life": in chapter 11: "He who believes in Me, even if he shall have died, shall live; and everyone who lives and believes in Me shall not die forever." He most fittingly describes the passion in relation to the figure, so that it may become more credible; and most fittingly did the figure precede, because, just as there they were not healed by the serpent unless they looked upon it, so neither are they healed through Christ unless they believe in Him. …

Commentary on John, Chapter 3 ↗