1 Samuel 27:9
And David smote the land, and left neither man nor woman alive, and took away the sheep, and the oxen, and the asses, and the camels, and the apparel, and returned, and came to Achish. And David smote the land, and left neither man nor woman alive, and took away the sheep, and the oxen, and the asses, and the camels, and the apparel, and returned, and came to Achish.
This verse belongs to the time when David's faith failed and, without seeking God's counsel, he placed himself under Philistine protection. The peoples he struck were the Geshurites, the Gezrites, and the Amalekites. He left neither man nor woman alive so that no survivors could report his actions to Achish, and he returned with the captured sheep and oxen and asses and camels and apparel. He concealed his true actions and gave Achish a false account, thus repaying the Philistines' kindness with deception.
The Philistines' welcome was selfish, for they hoped to use his forces against Saul and Israel. By that concealment he strengthened the Philistines by leading them to think Israel had turned against David. Although he was appointed to defend God's people and knew the Philistines were to be destroyed, in this course he was not following God's counsel. The verse teaches that God's servants should not reveal their people's weakness or appear indifferent to their welfare.