Isaiah 43:19

(Verses 18-19) Do not remember the former things, and do not consider the ancient things. Behold, I am doing something new, now it will spring forth; will you not know it? I will make a way in the wilderness, and rivers in the desert. LXX: Do not remember the former things, nor consider the things of old. Behold, I am doing a new thing; now it shall spring forth, shall you not know it? I will even make a way in the wilderness, and rivers in the desert.

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.…" There God foretold by the prophet that among the nations, in places that 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 children of God by the generation of baptism. Moreover, it is again predicted and foretold before, that the Jews, if they should thirst and seek after Christ, should drink with us, that is, should attain the grace of baptism. "If they shall thirst," he says, "he shall lead them through the deserts, shall bring forth water for them out of the rock. The rock shall be cloven, and the water shall flow, and my people shall drink," which is fulfilled in the Gospel, when Christ, who is the Rock, is cloven by a stroke of the spear in his passion; who also, admonishing what was before announced by the prophet, cries and says, "If anyone thirst, let him come and drink. He who believes in me, as the Scripture says, out of his belly shall flow rivers of living water." And that it might be more evident that the Lord is speaking there not of the cup but of baptism, the Scripture adds, saying, "But this spoke he of the Spirit, which they that believe in him should receive." For by baptism the Holy Spirit is received, and thus by those who are baptized and have attained to the Holy Spirit is attained the drinking of the Lord's cup.

Because of the newness of these things: behold I do new things, unheard of: behold, I make all things new (Rev 21:5); and because of their determination: I will make a way, for those going to the feasts, in the wilderness, that is, the land …

A new thing - Such a work as was never yet done in the world. Now - The scripture often speaks of things at a great distance of time, as if they were now at hand; to make us sensible of the inconsiderableness of time, and all temporal things, in comparison of God, and eternal things; upon which account it is said, that a thousand years are in God's sight but as one day.

Behold, I will do a new thing,....

A method taken to prepare the people for their deliverance, by putting them in mind of their sins, by which they had provoked God to send them into captivity and continue them there, that they might repent and seek to God for pardoning mercy,

Behold, I will do a new thing - At Isa 43:16, the prophet had referred to the deliverance from Egypt and the passage through the Red Sea; here he promises that the same power shall be employed in their redemption and return from the Babylonish captivity. This was to be a new prodigy.

I will do a new thing - Something that has not hitherto occurred, some unheard of and wonderful event, that shall far surpass all that he had formerly done (see the note at Isa 42:9). Now it shall spring forth - (See the note at Isa 42:9). It shall spring up as the grass does from the earth; or it shall bud forth like the opening leaves and flowers - a beautiful figure, denoting the manner in which the events of Divine Providence come to pass.