John Gill Commentary Joshua 9:15

"And Joshua made peace with them, and made a covenant with them, to let them live: and the princes of the congregation sware unto them." — Joshua 9:15 (ASV)

And Joshua made peace with them Upon the report the princes made of having examined what they had said, and which they found to be true, particularly concerning their victuals:

and made a league with them, to let them live ; and not destroy them as he did the Canaanites, and was ordered to do; they being supposed not to belong to them by the representation of things they had made:

and the princes of the congregation sware unto them ; that they would keep the league and covenant they had made with them inviolable; they ratified it by an oath, which was a sacred solemn thing.