1 Samuel 24:19
For if a man find his enemy, will he let him go well away? wherefore the LORD reward thee good for that thou hast done unto me this day. For if a man find his enemy, will he let him go well away? wherefore the LORD reward thee good for that thou hast done unto me this day.
The encounter recorded in 1 Samuel 24:1-22 sets a shepherd lad holding God's promise of the throne against an established monarch bent on holding fast his power. David stood utterly helpless in himself, yet by trusting God's word he withstood the power of the whole world. His course witnesses to the power of God's word prevailing over all human power and policy enlisted in support of evil.
Saul's own question admits the facts, that he was David's enemy, that David found him with the opportunity to kill him, and that David let him go unharmed. No one who finds his enemy would ordinarily let him go safely away. Saul therefore confessed that David had repaid his evil with good that day. For that goodness he asked the Lord to reward David with good.