1 Samuel 29 · a question people ask
Why did Achish trust David so completely?
The chapter gives Achish's words, not the reasons behind them. He calls David "the servant of Saul the king of Israel, who has been with me these days, or rather these years" (29:3), and says, "I have found no fault in him since he fell away until today" (29:3). He swears it to David: "As the LORD lives, you have been upright" (29:6). Two chapters back, the book shows what Achish had been told. When he asked David where he had raided, David named the South of Judah, of the Jerahmeelites and of the Kenites (27:10), and "Achish believed David" (27:12), saying, "He has made his people Israel utterly to abhor him. Therefore he will be my servant forever" (27:12). The book counts David's time in the country of the Philistines as "a full year and four months" (27:7). Past that, the text doesn't say why Achish trusted him, and this answer doesn't either.
The verses
“Then the princes of the Philistines said, “What about these Hebrews?” Achish said to the princes of the Philistines, “Isn’t this David, the servant of Saul the king of Israel, who has been with me these days, or rather these years? I have found no fault in him since he fell away until today.””
“Then Achish called David and said to him, “As the LORD lives, you have been upright, and your going out and your coming in with me in the army is good in my sight; for I have not found evil in you since the day of your coming to me to this day. Nevertheless, the lords don’t favor you.”
“The number of the days that David lived in the country of the Philistines was a full year and four months.”
“Achish said, “Against whom have you made a raid today?” David said, “Against the South of Judah, against the South of the Jerahmeelites, and against the South of the Kenites.””