Notes on the Bible, by Albert Barnes, , at sacred-texts.com
Shechem, situated between those mountains, Ebal and Gerizim, which had already been the scene of a solemn rehearsal of the covenant soon after the first entry of the people into the promised land Jos 8:30-35, was a fitting scene for the solemn renewal on the part of the people of that covenant with God which had been on His part so signally and so fully kept. The spot itself suggested the allusions to Abraham, Isaac, and Jacob, etc., in Joshua's address; and its associations could not but give special force and moving effect to his appeals. This address was not made to the rulers only but to the whole nation, not of course to the tribes assembled in mass, but to their representatives.
The other side of the flood - Better "On the other side of the river," i. e. the Euphrates. See the marginal reference.
They served other gods - Possibly the "images," or teraphim, which we find their ancestor Laban calling "his gods" (see the marginal reference); and of which it would seem that there were, as Joshua spoke, some secret devotees among the people Jos 24:14, Jos 24:25. It is not stated that Abraham himself was an idolater, though his fathers were. Jewish tradition asserts that Abraham while in Ur of the Chaldees was persecuted for his abhorrence of idolatry, and hence, was called away by God from his native land. The reference in the text to the original state of those who were the forefathers of the nation, is made to show that they were no better than others: God chose them not for their excellences but of His own mere motion.
Choose - Service of God in sincerity and truth can only result from a free and willing allegiance of the heart. This accordingly is what Joshua invites, as Moses had done before him (Deu 30:15 ff).
Made a covenant with the people - i. e. he solemnly ratified and renewed the covenant of Sinai, as Moses had done before him Deu 29:1. As no new or different covenant was made, no sacrifices were necessary.
Consult the marginal references.
That was by the sanctuary of the Lord - i. e. the spot where Abraham and Jacob had sacrificed and worshipped, and which might well be regarded by their posterity as a holy place or sanctuary. Perhaps the very altar of Abraham and Jacob was still remaining.
(Eleazar's burial-place is placed by Conder not at Tibneh but in the village of 'Awertah.)