Under the new covenant of Jeremiah 31, where will God write His law?

Answer: On their hearts

"I will put My law in their minds and inscribe it on their hearts. And I will be their God, and they will be My people."

““But this is the covenant I will make with the house of Israel after those days, declares the LORD. I will put My law in their minds and inscribe it on their hearts. And I will be their God, and they will be My people.”— Jeremiah 31:33 (BSB)