Flavius Josephus, Antiquities of the Jews
William Whiston, A.M., Ed.

[351] Now when the Philistines, as I said before, had pitched their camp, and had taken an account of their forces, according to their nations, and kingdoms, and governments, king Achish came last of all with his own army; after whom came David with his six hundred armed men. And when the commanders of the Philistines saw him, they asked the king whence these Hebrews came, and at whose invitation. He answered that it was David, who was fled away from his master Saul, and that he had entertained him when he came to him, and that now he was willing to make him this requital for his favors, and to avenge himself upon Saul, and so was become his confederate. The commanders complained of this, that he had taken him for a confederate who was an enemy; and gave him counsel to send him away, lest he should unawares do his friends a great deal of mischief by entertaining him, for that he afforded him an opportunity of being reconciled to his master by doing a mischief to our army. They thereupon desired him, out of a prudent foresight of this, to send him away, with his six hundred armed men, to the place he had given him for his habitation; for that this was that David whom the virgins celebrated in their hymns, as having destroyed many ten thousands of the Philistines. When the king of Gath heard this, he thought they spake well; so he called David, and said to him, "As for myself, I can bear witness that thou hast shown great diligence and kindness about me, and on that account it was that I took thee for my confederate; however, what I have done does not please the commanders of the Philistines; go therefore within a day's time to the place I have given thee, without suspecting any harm, and there keep my country, lest any of our enemies should make an incursion upon it, which will be one part of that assistance which I expect from thee." So David came to Ziklag, as the king of Gath bade him; but it happened, that while he was gone to the assistance of the Philistines, the Amalekites had made an incursion, and taken Ziklag before, and had burnt it; and when they had taken a great deal of other prey out of that place, and out of the other parts of the Philistines' country, they departed.