1 Samuel 20:5

The new moon. — On the religious ceremonies connected with the day of the new moon at the beginning of each month, see the Mosaic enactments in Números 10:10; Números 28:11.

At the court of Saul the feast seems to have been carefully observed, doubtless with the blast of trumpets, and with solemn burnt offerings and sin offerings, for we notice in this narrative that the plea of possible ceremonial uncleanness was at once accepted as an excuse for absence. (See 1 Samuel 20:26.)

The sacrificial and ceremonial rites were accompanied by a state and family banquet, at which David, as the king’s son-in-law, and also as holding a high post in the royal army, was expected to be present.
Jonathan persisted in looking upon his father’s later designs against the life of David as simply frenzied acts, incident upon his distressing malady, and evidently believed that after his strange seizure at Ramah he would return, and treat David with the confidence of old days when he met him at the feast of the new moon. David, however, believed otherwise, and was convinced, to use his own expressive words, that there was but a step between him and death. He would not trust himself, therefore, to Saul’s hands until his friend had made the experiment he suggested.