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

[71] WHEN the Philistines understood that David was made king of the Hebrews, they made war against him at Jerusalem; and when they had seized upon that valley which is called The Valley of the Giants, and is a place not far from the city, they pitched their camp therein; but the king of the Jews, who never permitted himself to do any thing without prophecy, ¹ and the command of God and without depending on him as a security for the time to come, bade the high priest to foretell to him what was the will of God, and what would be the event of this battle. And when he foretold that he should gain the victory and the dominion, he led out his army against the Philistines; and when the battle was joined, he came himself behind, and fell upon the enemy on the sudden, and slew some of them, and put the rest to flight. And let no one suppose that it was a small army of the Philistines that came against the Hebrews, as guessing so from the suddenness of their defeat, and from their having performed no great action, or that was worth recording, from the slowness of their march, and want of courage; but let him know that all Syria and Phoenicia, with many other nations besides them, and those warlike nations also, came to their assistance, and had a share in this war, which thing was the only cause why, when they had been so often conquered, and had lost so many ten thousands of their men, they still came upon the Hebrews with greater armies; nay, indeed, when they had so often failed of their purpose in these battles, they came upon David with an army three times as numerous as before, and pitched their camp on the same spot of ground as before. The king of Israel therefore inquired of God again concerning the event of the battle; and the high priest prophesied to him, that he should keep his army in the groves, called the Groves of Weeping, which were not far from the enemy's camp, and that he should not move, nor begin to fight, till the trees of the grove should be in motion without the wind's blowing; but as soon as these trees moved, and the time foretold to him by God was come, he should, without delay, go out to gain what was an already prepared and evident victory; for the several ranks of the enemy's army did not sustain him, but retreated at the first onset, whom he closely followed, and slew them as he went along, and pursued them to the city Gaza (which is the limit of their country): after this he spoiled their camp, in which he found great riches; and he destroyed their gods.