1 Samuel 30:17

And David smote them, &c.— The number of Amalekites that fled, was equal to that of all David's forces; and out of self-preservation, he was obliged to put as many of them to the sword as he could, to prevent being surrounded and destroyed by so superior a number. A partial victory, instead of being of any service to him, would have rather turned out to his disadvantage; because the straggling parties might have united, and watched an opportunity of retrieving their defeat by a second attack; and it was not unknown to David, nor can it be unknown to any impartial reader, that the Amalekites were such inveterate enemies to the Israelites, and so restless at the same time, that they would have lost no opportunity of wiping off their disgrace, or endangering the very being of the Israelitish nation. I affirm, lastly, that David not only acted prudently, but well, in pursuing his victory, and extirpating them, as they were proscribed by God himself, and condemned to be utterly cut off.