Complete Commentary on the Whole Bible, by Matthew Henry, at sacred-texts.com
1 Kings (1 Samuel) Chapter 21
(Sa1 21:1-9) David with Ahimelech.
(Sa1 21:10-15) David at Gath feigns himself mad.
David, in distress, fled to the tabernacle of God. It is great comfort in a day of trouble, that we have a God to go to, to whom we may open our cases, and from whom we may ask and expect direction. David told Ahimelech a gross untruth. What shall we say to this? The Scripture does not conceal it, and we dare not justify it; it was ill done, and proved of bad consequence; for it occasioned the death of the priests of the Lord. David thought upon it afterward with regret. David had great faith and courage, yet both failed him; he fell thus foully through fear and cowardice, and owing to the weakness of his faith. Had he trusted God aright, he would not have used such a sorry, sinful shift for his own preservation. It is written, not for us to do the like, no, not in the greatest straits, but for our warning. David asked of Ahimelech bread and a sword. Ahimelech supposed they might eat the shew-bread. The Son of David taught from it, that mercy is to be preferred to sacrifice; that ritual observances must give way to moral duties. Doeg set his foot as far within the tabernacle as David did. We little know with what hearts people come to the house of God, nor what use they will make of pretended devotion. If many come in simplicity of heart to serve their God, others come to observe their teachers and to prove accusers. Only God and the event can distinguish between a David and a Doeg, when both are in the tabernacle.
God's persecuted people have often found better usage from Philistines than from Israelites. David had reason to put confidence in Achish, yet he began to be afraid. His conduct was degrading, and discovered wavering in his faith and courage. The more simply we depend on God, and obey him, the more comfortably and surely we shall walk through this troublesome world.