Ambrose of Milan

(de Sacr. iv. 4.) This bread before the sacramentary words, is the bread in common use; after consecration it is made of bread Christ’s flesh. And what are the words, or whose are the phrases of consecration, save those of the Lord Jesus? For if His word had power to make those things begin to be which were not, how much rather will it not be efficacious to cause them to remain what they are, while they are at the same time changed into somewhat else? For if the heavenly word has been effectual in other matters, is it ineffectual in heavenly sacraments? Therefore of the bread is made the Body of Christ, and the wine is made blood by the consecration of the heavenly word.f Dost thou enquire after the manner? Learn. The course of nature is, that a man is not born but of man and woman, but by God’s will Christ was born of the Holy Spirit and a Virgin.