Albert Barnes Commentary 2 Samuel 21:4

"And the Gibeonites said unto him, It is no matter of silver or gold between us and Saul, or his house; neither is it for us to put any man to death in Israel. And he said, What ye shall say, that will I do for you." — 2 Samuel 21:4 (ASV)

No silver, nor gold... - Money payments as compensation for blood-guilt were very common among many nations. The law, too, in Numbers 35:31-32, presupposes the existence of the custom which it prohibits. In like manner, the speech of the Gibeonites implies that such a payment as they refuse would be a not unusual proceeding.

Neither... shall you kill any man in Israel - They mean that it is not against the nation of Israel, but against the individual Saul, that they cry for vengeance. The demand for Saul’s sons is exactly similar to that which dictated David’s own expression in 2 Samuel 24:17: against me, and against my father’s house.