Exodus 20:24-25

24You shall make 1an altar of earth for Me, and you shall sacrifice on it your 2burnt offerings and your 3peace offerings, 4your sheep and your oxen; in every place 5where I cause My name to be remembered, I will come to you and bless you.

25And if you make an altar of stone for Me, 6you shall not build it of cut stones, for if you wield your chisel on it, you will profane it.