Albert Barnes Commentary Joshua 24:2

"And Joshua said unto all the people, Thus saith Jehovah, the God of Israel, Your fathers dwelt of old time beyond the River, even Terah, the father of Abraham, and the father of Nahor: and they served other gods." — Joshua 24:2 (ASV)

The other side of the flood - Better: “On the other side of the river,” that is, the Euphrates. See the marginal reference.

They served other gods - This possibly refers to the “images,” or teraphim, which we find their ancestor Laban calling “his gods” (see the marginal reference). It would also seem that, as Joshua spoke, there were some secret devotees among the people (Joshua 24:14; Joshua 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 therefore was called away by God from his native land.

The reference in the text to the original state of the nation's forefathers is made to show that they were no better than others: God chose them not for their excellences but by His own sovereign will.