As Moses the servant of the Lord commanded the children of Israel, as it is written in the book of the law of Moses, an altar of whole stones, over which no man hath lift up any iron: and they offered thereon burnt offerings unto the Lord, and sacrificed peace offerings. (Joshua 8:31)
This was in harmony with God’s command (Deut. 27:5, 6). The reason for the use of “whole stones” was that there was danger that by the use of the chisel the Israelites might fashion for themselves images upon these altars, and thus be tempted to idolatry (see on Ex. 20:25).