2 Samuel 21:7
But the king spared Mephibosheth, the son of Jonathan the son of Saul, because of the LORD’s oath that was between them, between David and Jonathan the son of Saul. But the king spared Mephibosheth, the son of Jonathan the son of Saul, because of the LORD’s oath that was between them, between David and Jonathan the son of Saul.
The king spared Mephibosheth, the son of Jonathan the son of Saul and thus Saul's grandson, because of the LORD's oath that had been made before the Lord between David and Jonathan. In the surrounding events David gave seven of Saul's descendants to the Gibeonites, and seven other sons of Saul were hanged at Gibeah, with two of those given up being Rizpah's sons. That giving up of the seven was an act of scriptural justice rather than revenge. The sparing of Mephibosheth shows that David's kindness to the house of Saul remained in evidence and was still in evidence.
The verse belongs to the later history of David that records the judgments following his great transgression, showing the fulfillment of Nathan's denunciation. The chapter teaches that God holds a people responsible together when many allow the transgressions of a few to continue. It is connected with God's hatred of oppression and His refusal to tolerate it even when it is directed against people outside the household of faith. The sparing illustrates the family bond, in that an obligation arising from one relationship could protect another member of that family.