Moses told the Israelites that when Jehovah brought them into the land that they were going to possess, they “must also give the blessing upon Mount Gerizim and the malediction upon Mount Ebal.” (De 11:29, 30) He also instructed that great uncut stones be selected, whitewashed with lime, and set on Mount Ebal. An altar was to be erected there, upon which sacrifices were to be presented to Jehovah. Moses also said, “You must write on the stones all the words of this law, making them quite clear.”​—De 27:1-8.

After Israel’s victory at Ai, Joshua complied with Moses’ instructions, building an altar to Jehovah in Mount Ebal. Upon stones (perhaps, but not necessarily, those of the altar itself) he wrote “a copy of the law of Moses that he had written before the sons of Israel.” Then, in front of the congregation of Israel (including the alien residents) assembled as Moses had directed, Joshua “read aloud all the words of the law, the blessing and the malediction, according to all that is written in the book of the law.” Half the congregation stood in front of Mount Ebal and the other half in front of Mount Gerizim, the ark of the covenant and the Levites being between the two groups. (Jos 8:30-35) The slopes of Mount Ebal in relation to the slopes of Mount Gerizim provided excellent acoustics for this occasion. Notably, too, these things occurred approximately in the heart of the land of promise and in the vicinity where Jehovah promised the land to Israel’s forefather Abram (Abraham).​—Ge 12:6, 7.