5 And there shalt thou build an altar. At their first entrance into the land, God commands that a sacrifice of thanksgiving should be offered to Him; and this Joshua performed, as is related in Joshua 8:30-31

"Then Joshua built an altar unto the Lord God of Israel in Mount Ebal;
as Moses the servant of the Lord commanded the children of Israel,
an altar of whole stones, over which no man hath lift up any iron."

First of all, then, this testimony of their gratitude is required, that the children of Israel, as soon as they have begun to set foot in the land of Canaan, might celebrate the praises of the Lord; secondly, he forbids all artificial work, because, if the altar had been permanent, it would have been an occasion of superstition, and this exceptional instance would have been more regarded than the perpetual Law of God. Hence the nine tribes and half were so greatly wroth against the two tribes of Reuben and Gad, and half Manasseh, on account of the altar which was built on the bank of Jordan, (Joshua 22,) insomuch that they determined utterly to destroy their brethren, until they had cleared themselves by alleging that they had only built it as a memorial of their brotherly union, and not for sacrifice. Assuredly they were good expounders of the Law who accounted it an inexpiable crime, that an altar should be left for posterity, to withdraw the people from the one sanctuary, and thus to destroy the unity of faith.