According to 1 Samuel, Saul’s son and David’s close friend was Jonathan.
Jonathan first appears as a courageous warrior and the eldest son of King Saul. After David’s victory over Goliath, Jonathan formed a close covenant friendship with him. The text says Jonathan loved David as himself and gave him his robe, armor, sword, bow, and belt as signs of their bond.
Jonathan repeatedly protected David from Saul’s hostility. He warned David about planned attacks and tried to persuade his father that David had done nothing deserving death. Their friendship created a powerful tension because Jonathan was Saul’s heir in the normal royal succession, while David had been chosen to become king.
Jonathan died alongside Saul and two of his brothers at Mount Gilboa in a battle against the Philistines. David later mourned him in a famous lament and continued to honor his covenant with Jonathan by caring for Jonathan’s son Mephibosheth.