Jonathan appealed to the Lord in an oath indicating the seriousness of the situation (vv. 12, 13). He prayed that God would be with David as he had been with Saul, namely, as Israel's king (v. 13). These verses indicate clearly that Jonathan believed David would someday be king and subdue his enemies including Saul (vv. 13-15; cf. 13:14). He had come to appreciate Yahweh's loyal love (Heb. hesed, vv. 14, 15) and now called on David to deal similarly with his descendants in the future. He secured a promise from David that when he reigned he would protect Jonathan's family. "Lovingkindness"(Heb. hesed, vv. 14, 15) is a covenant term of commitment (v. 16, 42; cf. Deut. 7:7-9). Previously David and Jonathan had made a covenant that Jonathan would yield the throne to David and support him (18:3-4). Now David promised not to kill Jonathan's descendants after David became king. It was common in the ancient Near East for kings who began a new dynasty to kill all the descendants of the former king to keep them from rising up and trying to reclaim the throne. Jonathan called on God to require an accounting for antagonism at the hands of David's enemies (v. 16). This was the second vow that David had made after the one in which he pledged his love for Jonathan personally (v. 17; cf. 18:3-4).
