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.