"Jonathan took off the robe he was wearing and gave it to David, along with his tunic, and even his sword, his bow, and his belt" (1 Samuel 18:4).
In 1 Samuel 17, we read that the Philistines assembled to make war on Israel and sent out a giant named Goliath to represent them. Day after day he taunted Israel, demanding that they send someone to battle him one-on-one. Nobody, including King Saul, volunteered.
By contrast, David volunteered and was successful. The army of Israel followed David’s lead, and the Philistines were defeated. Saul asked to speak with David after the battle, apparently not realizing that David was the musician who had been playing for him. (Why this is so is puzzling; perhaps Saul’s insanity interfered with his memory.) Saul and his son Jonathan interviewed David, and Saul decided to bring David to the palace to live (1 Samuel 17:55–58; 18:1–2).
We are told that Jonathan loved David as himself (1 Samuel 18:3), and as a token of his affection gave David his royal robe, tunic, sword, bow, and belt. This act virtually adopted David into the family as a younger brother of Jonathan; in fact, this action was called a covenant (v. 3). It made David a potential heir to the throne. Later, Jonathan made it clear that he was ready to step aside so David might rule (1 Samuel 20:13–16, 31; 23:17).
Later in 1 Samuel 18, we see David being hailed by the people as a warrior greater than Saul. Obviously, this did not sit well with Saul (vv. 6–16). He offered his daughter Merab to David, if he continued to be successful in war. Saul hoped that David, by aggressively pursuing war, would die; after all, if David married a royal princess, he would come even closer to the crown. As David’s victories mounted, Saul quickly married off Merab to another man (vv. 17–19).
Saul’s younger daughter, Michal, loved David. Here we see the affections of Saul’s household shifting from him to David. Saul decided to exploit this romance by asking David to kill 100 Philistines as a dowry—something only a Samson could do. But David showed himself a champion superior even to Samson by bringing proof of having killed 200 men. This time Saul could do little but permit the marriage (1 Samuel 18:20–29).
God did not put David on Saul’s throne through a revolution but by legal means. It was Saul who brought David into the palace; it was the crown prince who adopted him as a brother; it was a crown princess who loved and married him. When Jonathan died, David was the most logical heir apparent to the throne. Trace how God has maneuvered you into your current position in life.