Exodus 20:25
If you make me an altar of stone, you must not build it of stones shaped with tools, for if you use your tool on it you have defiled it.
Deuteronomy 27:5-6
Then you must build an altar there to the Lord your God, an altar of stones -- do not use an iron tool on them.
Joshua 8:31
just as Moses the Lord's servant had commanded the Israelites. As described in the law scroll of Moses, it was made with uncut stones untouched by an iron tool. They offered burnt sacrifices on it and sacrificed tokens of peace.
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
Then you must build an altar there to the Lord your God, an altar of stones -- do not use an iron tool on them.
Joshua 8:31
just as Moses the Lord's servant had commanded the Israelites. As described in the law scroll of Moses, it was made with uncut stones untouched by an iron tool. They offered burnt sacrifices on it and sacrificed tokens of peace.
General references
Leviticus 16:33
and he is to purify the Most Holy Place, he is to purify the Meeting Tent and the altar, and he is to make atonement for the priests and for all the people of the assembly.