Now the Gibeonites were not of the people of Israel but of the remnant of the Amorites. Although the people of Israel had sworn to spare them, Saul had sought to strike them down in his zeal for the people of Israel and Judah. - 2 Samuel 21:2
Saul puts the Gibeonites to death
At some point, he put the Gibeonites to death. (2 Samuel 21:1-5)
Resolving Saul's house's bloodguilt
There was a famine in Israel during King David's reign, and when David sought the LORD, he said, "There is bloodguilt on Saul and on his house, because he put the Gibeonites to death.” When David called the Gibeonites, they said, "It is not a 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." When David asked what to do for them, they said, "The man who consumed us and planned to destroy us, so that we should have no place in all the territory of Israel, let seven of his sons be given to us, so that we may hang them before the Lord at Gibeah of Saul, the chosen of the Lord." David agreed to the terms but spared Jonathan's son Mephibosheth, giving 2 sons of Saul and Rizpah the daughter of Aiah and 5 sons of Adriel the son of Barzillai the Meholathite and Merab.