Matthew Henry Commentary 1 Samuel 27:8-12

"And David and his men went up, and made a raid upon the Geshurites, and the Girzites, and the Amalekites; for those [nations] were the inhabitants of the land, who were of old, as thou goest to Shur, even unto the land of Egypt. And David smote the land, and saved neither man nor woman alive, and took away the sheep, and the oxen, and the asses, and the camels, and the apparel; and he returned, and came to Achish. And Achish said, Against whom have ye made a raid to-day? And David said, Against the South of Judah, and against the South of the Jerahmeelites, and against the South of the Kenites. 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. And Achish believed David, saying, He hath made his people Israel utterly to abhor him; therefore he shall be my servant for ever." — 1 Samuel 27:8-12 (ASV)

While David was in the land of the Philistines, he attacked some remnants of the devoted nations. The people whom he destroyed had long before been doomed to destruction. It is often wise to shun public notice, but we must in no situation be idle. We must always try to do something in the cause of God.

David hid this expedition from Achish. But an equivocation which serves the purpose of a lie is as similar to it as a hypocrite is to a profane person; it is only better in appearance, therefore more dangerous. Yet, though believers often manifest imperfections, they can never be persuaded to renounce the service of God, to unite their interests with His enemies, or finally to become the servants of sin and Satan.

But what a train of evils follows from unbelief! When we forget the Lord's past mercies and His gracious assurances, we will be overwhelmed with desponding fears and probably be led to adopt some dishonourable method to get rid of our troubles. Nothing can so effectively establish us in holy dispositions and practices, and preserve us from perplexities, as firm, unshaken dependence upon the promises of God in Christ Jesus.