Deuteronomy 27:5-6

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.

There shalt thou build an altar ... of whole stones. The stones were to be in their natural state, as if a chisel would communicate pollution to them. It is not certain whether the same stones formed the monument on the sides of which the words of the law were inscribed, as well as the altar on which the victims were sacrificed that signalized its renewed ratification (see the note at Joshua 8:30). At all events, the stony pile was so large as to contain all the conditions of the covenant, so elevated as to be visible to the whole congregation of Israel; and the religious ceremonial performed around it on the occasion was solemn and impressive, consisting, first, of the elementary worship needed for sinful men; and secondly, of the peace offerings, or lively social feasts that were suited to the happy people whose God was the Lord. There were thus the law which condemned and the typical expiation-the two great principles of revealed religion.