1 Samuel 29:8
And David said unto Achish, But what have I done? and what hast thou found in thy servant so long as I have been with thee unto this day, that I may not go fight against the enemies of my lord the king? And David said unto Achish, But what have I done? and what hast thou found in thy servant so long as I have been with thee unto this day, that I may not go fight against the enemies of my lord the king?
In the verse David asks Achish what he has done and what fault has been found in him during his service up to that day, and why he may not go to fight against the king's enemies. He addresses Achish as his lord and king and presents himself as a loyal servant eager to fight alongside him. The setting is the fear of the Philistine princes that David might turn against them in the battle and aid Israel.
David was expected to fight for the Philistines, so withdrawing on his own would have made him appear cowardly, ungrateful, and treacherous. Yet he could not fight against Israel, for that would make him a traitor to his country and to God's people. It would also ruin his claim to Israel's throne and leave him blamed if Saul died in the battle.
His words conceal his true feelings and show how entangled he had become in deception. Achish's reply brought that entanglement home to him with shame and remorse.