1 Samuel 24:21
Swear now therefore unto me by the LORD, that thou wilt not cut off my seed after me, and that thou wilt not destroy my name out of my father’s house. Swear now therefore unto me by the LORD, that thou wilt not cut off my seed after me, and that thou wilt not destroy my name out of my father’s house.
The encounter belongs to the stand between David and Saul, with David as the shepherd youth to whom God had promised the throne and Saul as the reigning monarch determined to hold onto his power, looking ahead to the time when David would be king. In that setting Saul asks David to swear by the Lord that he will not cut off his descendants after him nor destroy his name from his father's house. David enters a covenant to show favor to Saul's house and to spare its name.
Though utterly helpless in himself, David trusted God's word in this stand and withstood the power of the whole world. That trust shows that God's word is stronger than human power and policy used to uphold evil. Such faith places David among the world's true nobility, its royal line. Young people today are called to take their place in that line.