Charles Ellicott Commentary 1 Samuel 30:9

"So David went, he and the six hundred men that were with him, and came to the brook Besor, where those that were left behind stayed." — 1 Samuel 30:9 (ASV)

So David went. Immediately on receiving the answer of the Urim, David started in rapid pursuit. The “six hundred” by no means represented his present force; but these were probably the old band of veteran soldiers, whose speed and endurance he could depend upon—men tried, no doubt, by many a weary night march, by many a rough, wild piece of work. A large contingent even of these veterans could not stand the forced march of their leader on this occasion.

In the words “for two hundred abode behind,” the narrator anticipated what is told in 1 Samuel 30:10. It is a proleptical expression, arising from the vivacious description of David’s rapid march with four hundred men (Lange). The Vulgate paraphrases, or rather seeks to amend the text here: “and certain tired ones stayed.” The Syriac changes the text into “David left two hundred men;” these men who had fallen out of the rapid march were gathered together, and kept the baggage and everything that could be left behind at the encampment at the brook Besor.

It is supposed that due to the hurried departure, scanty provision was made for the forced march, hence their falling out from weariness during the rapid advance. The brook Besor cannot be identified with certainty; and Raumer (Palestine) supposes it to be the Wady Shariah, which falls into the sea below Askelon.