Thomas Aquinas Commentary Jeremiah 31:35-37

"Thus saith Jehovah, who giveth the sun for a light by day, and the ordinances of the moon and of the stars for a light by night, who stirreth up the sea, so that the waves thereof roar; Jehovah of hosts is his name: If these ordinances depart from before me, saith Jehovah, then the seed of Israel also shall cease from being a nation before me for ever. Thus saith Jehovah: If heaven above can be measured, and the foundations of the earth searched out beneath, then will I also cast off all the seed of Israel for all that they have done, saith Jehovah." — Jeremiah 31:35-37 (ASV)

1. Here the confirmation of the promise is given.

2. He confirms it by the immutability of created things when he displays the power of the one who promises: who gives the sun as the light of the day. Who makes the great lights, the sun to rule the day, and the moon and the stars to rule the night (Psalms 135:8–9). It is as if he were saying, “He who made these things immovable will also be able to make His promise sure.”

   He then gives a comparison: if these laws fail. It is as if he were saying, “Just as they will not fail until the end of the world, so neither will the seed of Israel fail, with regard to those who are saved.” As the new heavens, and the new earth, which I make to stand before me, says the Lord, so shall your seed, and your name stand (Isaiah 66:22).

3. From the immensity of created things: thus says the Lord.

   1. He describes the impossibility of measuring them: if the heavens above can be measured by human ability. Who has measured with his fist the waters, and weighed the heavens with his palm? (Isaiah 40:12).

   2. He presents the promise: I also shall cast away. It is as if he were saying, “As that is impossible, so also is this”: the whole seed, because He has cast away some of them. For he has not willingly afflicted, nor cast off the children of men (Lamentations 3:33).