1 Samuel 25:39
And when David heard that Nabal was dead, he said, Blessed be the LORD, that hath pleaded the cause of my reproach from the hand of Nabal, and hath kept his servant from evil: for the LORD hath returned the wickedness of Nabal upon his own head. And David sent and communed with Abigail, to take her to him to wife.
Nabal's name signifies fool, and his story in 1 Samuel 25:1-44 stands as an illustration of selfish covetousness. When David heard that Nabal was dead, he blessed the Lord for pleading the cause of his reproach and judging the insult and wrong Nabal had done him. The Lord had kept His servant from evil by restraining him from taking revenge into his own hands. The Lord had returned Nabal's wickedness upon his own head.
After Nabal died, David sent and communed with Abigail to take her to him as his wife. She is recorded in 1 Samuel 25:39-42 as David's second wife, whom he sent for and married after Nabal's death. The whole chapter shows David facing personal persecution without seeking to destroy his persecutor, refusing to retaliate.
The verse reveals David's hope and trust in God and his utter refusal to avenge his own reproach, leaving his enemies to God's dealing rather than taking vengeance into his own hands. It is safe to leave one's cause in God's hands.