Exod 4:2

“But we know that prophecy expressed itself by things no less than by words. By words and also by deeds is the resurrection foretold. When Moses puts his hand into his bosom and then draws it out again dead, and again puts his hand into his bosom and plucks it out living, does not this apply as an anticipation of the resurrection to all humankind?—inasmuch as those three signs denoted the threefold power of God: when it shall, first, in the appointed order, subdue to man the old serpent, the devil, however formidable; then, second, draw forth the flesh from the bosom of death; and then, at last, shall pursue all blood [shed] in judgment.”

“Let me try to explain, as far as the Lord enables me to, what these signs mean. The rod stands for the kingdom, the snake for mortality; it was by the snake that man was given death to drink. The Lord was prepared to take this death to himself. So when the rod came down to earth it had the form of a snake, because the kingdom of God, which is Jesus Christ, came down to earth. He put on mortality, which he also nailed to the cross. Your holinesses know that when that proud and stiff-necked people grumbled against God in the desert, they began to be bitten by serpents and to die of the bites. In his mercy God provided a remedy, a remedy that restored health at the time but also foretold the wisdom that was to come in the future.”

“That staff, dearly beloved, prefigured the mystery of the cross. Just as through the staff Egypt was struck by ten plagues, so also the whole world was humiliated and conquered by the cross. Just as Pharaoh and his people were afflicted by the power of the staff, with the result that he released the Jewish people to serve God, so the devil and his angels are wearied and oppressed by the mystery of the cross to such an extent that they cannot recall the Christian people from God's service.”