On The Holy Trinity by St. Augustine
Chapter 5.--Why Miracles are Not Usual Works.
11. For since the divine power administers the whole spiritual and corporeal creature, the waters of the sea are summoned and poured out upon the face of the earth on certain days of every year. But when this was done at the prayer of the holy Elijah; because so continued and long a course of fair weather had gone before, that men were famished; and because at that very hour, in which the servant of God prayed, the air itself had not, by any moist aspect, put forth signs of the coming rain; the divine power was apparent in the great and rapid showers that followed, and by which that miracle was granted and dispensed. In like manner, God works ordinarily through thunders and lightnings: but because these were wrought in an unusual manner on Mount Sinai, and those sounds were not uttered with a confused noise, but so that it appeared by most sure proofs that certain intimations were given by them, they were miracles. Who draws up the sap through the root of the vine to the bunch of grapes, and makes the wine, except God; who, while man plants and waters, Himself giveth the increase? But when, at the command of the Lord, the water was turned into wine with an extraordinary quickness, the divine power was made manifest, by the confession even of the foolish. Who ordinarily clothes the trees with leaves and flowers except God? Yet, when the rod of Aaron the priest blossomed, the Godhead in some way conversed with doubting humanity. Again, the earthy matter certainly serves in common to the production and formation both of all kinds of wood and of the flesh of all animals: and who makes these things, but He who said, Let the earth bring them forth; and who governs and guides by the same word of His, those things which He has created? Yet, when He changed the same matter out of the rod of Moses into the flesh of a serpent, immediately and quickly, that change, which was unusual, although of a thing which was changeable, was a miracle. But who is it that gives life to every living thing at its birth, unless He who gave life to that serpent also for the moment, as there was need.