Joshua 9:15

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.