Jonathan and David made a covenant, something that was to be kept and fulfilled to the uttermost (v. 3a).
In order to equip David, Jonathan gave him his robe, armor, sword, bow, and belt (v. 4).
Saul took David and would not let him return to his father's house (v. 2). This is a further indication that God had prepared all the details concerning David's environment.
David was successful in every mission that Saul sent him on (v. 5a). The secret of David's success was his wisdom. Even as a youth, he behaved in a very wise way. For example, when his oldest brother condemned him for coming to the camp of the Israelites, he asked his brother, "Is there no cause?" (17:29). He realized that there was a cause from God and that God had prepared him and sent him. God had sovereignly put him in the field to take care of sheep, and God used the attack of the lion and the bear to train, prepare, and equip him to kill Goliath. David was also very experienced in speaking and in confronting people. His youth had been full of experiences which were the basis for his assurance in relation to Goliath. It is not an insignificant thing for a teen-ager to kill a lion or a bear. As a youth David gained this experience. Therefore, he was not afraid of Goliath.
Because David acted wisely, Saul set him over the men of battle, and it was good in the sight of all the people and also in the sight of Saul's servants (18:5b). Whatever Saul did to David became a good opportunity for David to gain favor with the people.