Why did Saul want to kill David when David did not do anything against him?

Saul’s final years were profoundly tragic as he endured periods of deep manic depression. However, it was a young man brought into the king’s court named David who became the soothing influence on the troubled king by playing music that temporarily restored the king’s sanity. The king embraced David as one of his own, but all of this changed as David became a fine military leader in his own right. In fact, a popular song of the day was “Saul has slain his thousands, and David his tens of thousands” (1 Samuel 18:7). When Saul realized that God was with David, the king sought to kill David at every opportunity. David succeeded in evading the countless attempts on his life with the help of the king’s son, Jonathan, and the king’s daughter, Michal.

The final years of King Saul’s life brought a general decline in his service to the nation and in his personal fortunes. He spent much time, energy, and expense trying to kill David rather than consolidating the gains of his earlier victories, and because of this the Philistines sensed an opening for a major victory over Israel. After Samuel’s death, the Philistine army gathered against Israel. Saul was terrified and tried to inquire of the Lord, but received no answer through the Urim or the prophets. Though he had banished mediums and spiritists from the land, Saul disguised himself and inquired of a medium in Endor. He asked her to contact Samuel. The Philistines routed Israel and kiled Saul’s sons, including Jonathan. Saul was critically wounded and asked his armor-bearer to kill him so that the Philistines would not torture him. In fear, Saul’s armor-bearer refused, so Saul fell on his own sword, followed by his armor-bearer who did the same.