Deuteronomy 27:5

“And there shall thou build an altar to the Lord thy God, etc.] On the same mountain, though not of the same stones. Jarchi’s note is, “after that (the setting up of the plastered stones) thou shalt bring from thence (from Jordan) others, and build of them an altar on Mount Ebal;” but Josephus f484 places this altar not on Mount Ebal, but between that and Gerizim. This altar, he says, was ordered to be built towards the rising sun, not far from the city of Shechem, between two mountains, Gerizim and Ebal; but the text is express, that it was to be built where the stones were set up, which was on Mount Ebal, and there it was built, (<060830>Joshua 8:30); an altar of stones; of whole stones, as…”

“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. The stony pile was to be 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 on the occasion was to consist: 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.”

“27:5 natural, uncut stones: Archaeological research has uncovered a number of Canaanite altars, all built of hewn blocks. In contrast to this practice, the Israelites were to build their altars only of rough field stones (Exod 20:22-26; see “Altars” Theme Note).”

“And there: Exo 24:4; Jos 8:30, Jos 8:31; Kg1 18:31, Kg1 18:32 thou shalt not: Exo 20:25 Deuteronomy 27:6”