Even though Saul tries again and again to kill David, David does not avenge himself on Saul because God had chosen Saul as king. This is meant to contrast with Saul's treatment of David, the future king. Saul represents the king the people wanted, a selfish man. David is the king God wanted, a godly man. (See: [[rc://en/tw/dict/bible/other/avenge]], [[rc://en/tw/dict/bible/kt/elect]] and [[rc://en/tw/dict/bible/kt/godly]])