Tertullian, On Baptism 9

How many natural safeguards, how many gracious privileges, how many disciplinary rites, figures, prefigurings, and prayers have established water's sacred role? (Exodus 14:28) First, when the people marched out of Egypt and crossed the sea, they escaped Pharaoh's power, while the water swallowed the king and his entire army. What figure could more clearly mirror the sacrament of Baptism? Nations are freed from the world through water, leaving behind the devil, their former master, crushed beneath the flood. (Exodus 15:25) Again, Moses' wood healed water poisoned by bitterness, turning it sweet for the people's benefit. That wood was Christ, who cures the deadliest veins of a poisonous, bitter nature through the waters of Baptism. This is the water that flowed from the rock that traveled with the people. If the rock is Christ, then beyond doubt we see the water in Christ blessed for Baptism. How immense is water's grace before God and his Christ for confirming Baptism. Christ is never without water, since he himself was baptized in it. (John 2:1-11) He launched the first signs of his power with water at a wedding feast. (John 4:14) When he preaches, he calls the thirsty to his eternal water. When he teaches on love, he endorses a cup of water offered to a brother as a work of love. He regains strength at a well; he walks freely on the water, crosses it, and serves water to his disciples. He keeps testifying to Baptism up to his passion; when he is handed over to the cross, water intervenes — Pilate's washing hands prove it; when his side is pierced, water bursts out — the soldier's lance bears witness. (John 19:34)