While there are a few Psalms and other places in Scripture dealing with their relationship, the most prominent place to observe the relationship between these two men is 1 Samuel 15-31. The reader can see a definite shift in the narrative between 1 Samuel 15 and 16. Saul is rejected by the LORD in one chapter and the boy David is anointed by the Lord as the king to take his place. The readers of 1 Samuel are given clues to the rejection of Saul and the rise of David, but as the story played out in real-time it would have likely been far more jolting to David.
DAVID NABAL AND ABIGAIL
David said to Abigail, "Praise be to the LORD, the God of Israel, who has sent you today to meet me. May you be blessed for your good judgment and for keeping me from bloodshed this day and from avenging myself with my own hands.
REPENTANCE - DEALINGS OF GOD IN DAVID'S LIFE
David confessed his sin, received forgiveness from God, and knew God could still use his life.