The staff’s change into a serpent should not trouble those who love Christ, as though we were applying the meaning of the mystery to an inappropriate animal. Truth Himself does not reject this image in the Gospel, where He says, “Just as Moses lifted up the serpent in the wilderness, so must the Son of Man be lifted up.”
The reasoning is clear. If divine Scripture calls the father of sin a serpent, then what is born from the serpent must also be a serpent. It follows that sin bears the same name as the one who gave it birth. And the apostolic word testifies that the Lord became sin for us, clothing Himself with our nature that is subject to sin.
The riddle therefore fits the Lord. The serpent here signifies nothing other than sin; and since the Lord became sin for us, He becomes a serpent for our sake. In this way He can devour and consume the Egyptian serpents that the magicians brought to life.
Once this has happened, the serpent changes back into the staff. By this staff sinners are corrected, while those climbing the steep and difficult path of virtue find support, leaning on the staff of faith with hope in the good things ahead. For “faith is the assurance of what is hoped for.”
Someone who comes to understand these things becomes, quite plainly, a god to those who oppose the truth and are captivated by this material and unreal deception. For such people, even hearing about the One who truly is is dismissed as something worthless. Pharaoh says, “Who is He, that I should listen to His voice? I do not know the Lord.” People who live by the less rational senses value only what is material and bodily.
If a person is strengthened to this degree by the shining of the light and receives such power and authority against his opponents, then he is like an athlete who has trained thoroughly under his coach. Confident now in his strength, he strips for the contest against his enemies, holding that staff in his hand—that is, the word of faith—with which he is about to defeat the Egyptian serpents.
His foreign wife will also follow him. There is something in education from outside the faith that need not be rejected as a partner in bringing forth virtue. Moral and natural philosophy can at times become the companion, friend, and partner of the higher life, provided that the offspring it produces carries no stain of foreignness.
Unless this offspring is circumcised—that is, unless everything harmful and impure is cut away from it—the angel who meets them brings the fear of death. The wife appeases the angel by showing her child to be clean, cutting away the mark that identifies it as foreign.
I think the sequence of growth in virtue should now be clear to anyone who remembers the story. Our interpretation follows the sequence of the story’s riddles. There is something fleshly and uncircumcised among the teachings that philosophy gives birth to; once this is cut away, what remains belongs to the noble heritage of Israel.
For example, philosophy from outside the faith also says that the soul is immortal. That part of its offspring accords with reverence for God. But its teaching that the soul passes from body to body and changes from a rational nature into an irrational one is the fleshly and foreign foreskin. There are many other examples of the same kind. It says that God exists, but thinks He is material. It acknowledges Him as creator, but thinks He needs matter in order to create. It grants that He is good and powerful, yet in many things makes Him yield to the necessity of fate.
Why go through every example one by one? The good teachings found in philosophy outside the faith are repeatedly stained by absurd additions. Once those additions are cut away, the angel of God becomes gracious toward us and rejoices over us as genuine offspring of such teachings.