Matthew Poole and continuators on 1 Samuel 24:22

22 And David sware unto Saul : and Saul went home; but David and his men gat them up unto the hold .

Qu. How then could David destroy so many of Saul's Sons, 2 Sam. 21. 8? Ans. David could bind himself by his Oaths, but he could not bind God, to whose good pleasure all Promises, Vows, Oaths, must in all reason be submitted; and that was done by Gods command, and God was well pleased with it, 2 Sam. 21. 14. Nor is it to be supposed that David sware not to destroy any of them in case God should specially command it, or that should by miscarriage render themselves obnoxious to the Sword of Justice: but onely that he would not do it barely on his own private account, nor seek occasions of so doing.

To wit, of Engedi, v. 1. For having had so great and frequent experience of Saul's inconstancy, and malice, and perfidiousness, he would trust him no more.