Charles Spurgeon Commentary Jeremiah 31:33

"But this is the covenant that I will make with the house of Israel after those days, saith Jehovah: I will put my law in their inward parts, and in their heart will I write it; and I will be their God, and they shall be my people:" — Jeremiah 31:33 (ASV)

And will be their God, and they shall be my people.

You may have heard it said that Christ will not leave his people, but that his people may leave him; but in this promise the second contingency is provided for as well as the first.

But this shall be the covenant that I will make with the house of Israel; after those days, says the LORD, I will put my law in their inward parts, and write it in their hearts;"

Not on the tables of stone, not on the walls of the church, but "I will write it in their hearts;"