20:5 At the beginning of each month, the Israelites gathered to celebrate the new moon festival. While this was mainly a time to be enjoyed, it was also a way to dedicate the next month to God. Other nations had celebrations during the full moon and worshiped the moon itself. The Israelites, however, celebrated their festival at the time of the new moon, when the moon was not visible in the sky. This was an added precaution against false worship. Nothing in the creation is to be worshiped—only the Creator.
20:15 Jonathan asked David to keep a promise to treat his children kindly in the future. Years later David took great pains to fulfill this promise: He invited Jonathan’s son Mephibosheth into his palace to live (2 Samuel 9).
20:26 Because the new moon festival involved making a sacrifice to God (Numbers 28:11-15), those attending the feast had to be ceremonially clean according to God’s laws (Exodus 19:10; Leviticus 15; Numbers 19:11-22; also see the note on Joshua 3:5). This cleansing involved washing the body and clothes before approaching God to offer a sacrifice. The outward cleansing was a symbol of the inward desire for a purified heart and right relationship with God. Today our hearts are purified by faith in God through the death of Jesus Christ on our behalf (Hebrews 10:10, 22) and by reading and heeding God’s Word (John 17:17).
20:31, 32 Saul was still trying to secure his throne for future generations even though he had already been told his dynasty would end with him (13:13, 14). Even worse, he was trying to do this by sinful human means because he knew he would get no help from God. Jonathan could have made a move to become the next king by killing his rival, but he bypassed this opportunity because of his love for both God and David (23:16-18).