John Gill Commentary Joshua 9:19

"But all the princes said unto all the congregation, We have sworn unto them by Jehovah, the God of Israel: now therefore we may not touch them." — Joshua 9:19 (ASV)

But all the princes said to all the congregation
That is, all the princes that went to Gibeon addressed all the Israelites that were there:

we have sworn to them by the Lord God of Israel ;
by the Word of the Lord God, as the Targum; an oath is a solemn sacred thing, and not to be broken, and a good man will make conscience of it, and keep it, though he has sworn to his own hurt: and

now therefore we may not touch them ;
neither take away their lives nor their substance.