Exodus 20:22-26 - Instructions For Building Altars
22 And Jehovah saith unto Moses, 'Thus dost thou say unto the sons of Israel: Ye -- ye have seen that from the heavens I have spoken with you; 23 ye do not make with Me gods of silver, even gods of gold ye do not make to yourselves.
24 'An altar of earth thou dost make for Me, and thou hast sacrificed on it thy burnt-offerings and thy peace-offerings, thy flock and thy herd; in every place where I cause My name to be remembered I come in unto thee, and have blessed thee. 25 'And if an altar of stones thou dost make to Me, thou dost not build them of hewn work; when thy tool thou hast waved over it, then thou dost pollute it; 26 neither dost thou go up by steps on Mine altar, that thy nakedness be not revealed upon it.