Albert Barnes Commentary 1 Samuel 27:11

"And David saved neither man nor woman alive, to bring them to Gath, saying, Lest they should tell of us, saying, So did David, and so hath been his manner all the while he hath dwelt in the country of the Philistines." — 1 Samuel 27:11 (ASV)

Tidings - This word is not in the original text. The meaning is, rather, “to bring them to Gath” as captives and slaves. The prisoners taken would naturally have been part of the spoil, but David did not dare to bring them to Gath, fearing his deceit would be discovered. Obviously, these tribes were allies of the Philistines.