Isaias 43:20

14. And those of them who declare that God would make a new covenant with men, not such as that which He made with the fathers at Mount Horeb, and would give to men a new heart and a new spirit; and again, “And remember ye not the things of old: behold, I make new things which shall now arise, and ye shall know it; and I will make a way in the desert, and rivers in a dry land, to give drink to my chosen people, my people whom I have acquired, that they may show forth my praise,”, plainly announced that liberty which distinguishes the new covenant, and the new wine which is put into new bottles, [that is], the faith which is in Christ, by which He has proclaimed the way of righteousness sprung up in the desert, and the streams of the Holy Spirit in a dry land, to give water to the elect people of God, whom He has acquired, that they might show forth His praise, but not that they might bla …

Again, David expressly (or rather the Lord in the person of the saint, and the same from the foundation of the world is each one who at different periods is saved, and shall be saved by faith) says, “My heart was glad, and my tongue rejoiced, and my flesh shall still rest in hope. For Thou shalt not leave my soul in hell, nor wilt Thou give Thine holy one to see corruption. Thou hast made known to me the paths of life, Thou wilt make me full of joy in Thy presence.” As, then, the people was precious to the Lord, so also is the entire holy people; he also who is converted from the Gentiles, who was prophesied under the name of proselyte, along with the Jew. …

Surely to Sion He brings good tidings, and to Jerusalem peace and all blessings; He goes up into a mountain, and there spends a night in prayer, and He is indeed heard by the Father. Accordingly turn over the prophets, and learn therefrom His entire course. “Into the high mountain,” says Isaiah, “get Thee up, who bringest good tidings to Sion; lift up Thy voice with strength, who bringest good tidings to Jerusalem.” “They were mightily astonished at His doctrine; for He was teaching as one who had power.” And again: “Therefore, my people shall know my name in that day.” What name does the prophet mean , but Christ’s? “That I am He that doth speak, even I.” For it was He who used to speak in the prophets, the Word, the Creator’s Son. …

8. But as often as water is named alone in the Holy Scriptures, baptism is referred to, as we see intimated in Isaiah: “Remember not,” says he, “the former things, and consider not the things of old. Behold, I will do a new thing, which shall now spring forth; and ye shall know it. I will even make a way in the wilderness, and rivers in the dry place, to give drink to my elected people, my people whom I have purchased, that they might show forth my praise.” There God foretold by the prophet, that among the nations, in places which previously had been dry, rivers should afterwards flow plenteously, and should provide water for the elected people of God, that is, for those who were made sons of God by the generation of baptism. …

In Isaiah: “Therefore remember ye not the former things, neither reconsider the ancient things. Behold, I make new the things which shall now arise, and ye shall know it; and I will make in the desert a way, and rivers in a dry place, to give drink to my chosen race, my people whom I acquired, that they should show forth my praises.” In the same also: “If they thirst, He will lead them through the deserts; He will bring forth water from the rock; the rock shall be cloven, and the water shall flow: and my people shall drink.” Moreover, in the Gospel according to Matthew, John says: “I indeed baptize you with water unto repentance: but He that cometh after me is mightier than I, whose shoes I am not worthy to bear; He shall baptize you with the Holy Ghost, and with fire.” Also according to John: “Except a man be born of water, and of the Spirit, he cannot enter into the kingdom of God. …