Deuteronomy 27:5
"And there shalt thou build an altar unto the LORD thy God, an altar of stones: thou shalt not lift up any iron tool upon them."
Cross References (ranked by relevance)
Exodus 20:25
And if thou wilt make me an altar of stone, thou shalt not build it of hewn stone: for if thou lift up thy tool upon it, thou hast polluted it.
Exodus 24:4
And Moses wrote all the words of the LORD, and rose up early in the morning, and builded an altar under the hill, and twelve pillars, according to the twelve tribes of Israel.