Exodus 20:25
If you make a stone altar for Me, you must not build it out of cut stones. If you use your chisel on it, you will defile it.
Deuteronomy 27:5-6
Build an altar of stones there to the Lord your God—you must not use any iron tool on them.
Joshua 8:31
just as Moses the Lord’s servant had commanded the Israelites. He built it according to what is written in the book of the law of Moses: an altar of uncut stones on which no iron tool has been used.
Treasury of Scripture Knowledge
Summary
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.
General references
Bible References
And
Deuteronomy 27:5
Build an altar of stones there to the Lord your God—you must not use any iron tool on them.
Joshua 8:31
just as Moses the Lord’s servant had commanded the Israelites. He built it according to what is written in the book of the law of Moses: an altar of uncut stones on which no iron tool has been used. Then they offered burnt offerings to the Lord and sacrificed fellowship offerings on it.
General references
Leviticus 16:33
and purify the most holy place. He will purify the tent of meeting and the altar and will make atonement for the priests and all the people of the assembly.