Exodus 20:22-26 - Instructions For Building Altars
22 And the LORD said unto Moses, "Thus thou shalt say unto the children of Israel, 'Ye have seen how that I have talked with you from out of heaven. 23 Ye shall not make therefore with me gods of silver nor gods of gold: in no wise shall ye do it.
24 An altar of earth thou shalt make unto me and thereon offer thy burnt offerings and thy peace offerings, and thy sheep and thine oxen. And in all places where I shall put the remembrance of my name, thither I will come unto thee and bless thee. 25 But and if thou wilt make me an altar of stone, see thou make it not of hewed stone, for if thou lift up thy tool upon it, thou shalt pollute it. 26 Moreover thou shalt not go up with steps unto mine altar, that thy nakedness be not showed thereon.'"