Joshua 8:31

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.

Of whole stones - according to the instructions given to Moses (Exodus 20:25; Deuteronomy 27:5).

Over which no man hath lift up any iron - i:e., iron tool. The reason of this was, that every altar of the true God ought properly to have been built of earth (Exodus 20:24); and if it was constructed of stone, rough unhewn stones were to be employed. that it might retain both the appearance and nature of earth, since every bloody sacrifice was connected with sin and death, by which man, the creature of earth, is brought to earth again (Keil). Another and perhaps more urgent reason was, that the artificially-built altars of the pagan were frequently inscribed with the name or symbol of the god to whom they were dedicated, and their skies ornamented with bas-reliefs of gods, or sculptured figures of idolatrous rites and festive scenes.

They offered thereon burnt offerings ... and sacrificed peace offerings. This had been done when the covenant was established (Exodus 24:5); and by the observance of these federal rites (Deuteronomy 27:6) the covenant was solemnly renewed-the people were reconciled to God by the burnt offering, whilst, by this feast accompanying the peace or thank offering, a happy communion with God was enjoyed by all the families in Israel.