Rashi on the Former Prophets

And they came to the Nachal Besor. [The] six hundred men.
Some of them remained behind. When they reached the Nachal Besor, there were among them some who were faint, and some of those remained there.

Who were too exhausted. Who refrained; and I say that this is Aramaic, the translation of וְנֶהֶרְסוּ [=and they will be destroyed].

South of the Kerethite. To the south of the Philistines. We find elsewhere the Philistines being called the כְּרֵתִים nation [in] "the inhabitants of the seacoast the nation of כְּרֵתִים."

Of the next day. The Amaleikites are accustomed to being defeated on the second day [of battle], as it is stated, "tomorrow I will stand…" Therefore, it states, "on the(ir) next day."

All the sheep and cattle. Which the troop had captured from the south of Yehudah and from the south of Caleiv.
They led. Men who were leading and marching before those cattle, to honor and praise themselves, [by declaring,] 'This is Dovid's spoil.'

From that day on. [Literally 'from that day and above']. It is not stated: "[from that day] on" but "[from that day] and above [=before]." Avrohom had already instituted this statute [when he said,] "Only what the lads have eaten," those are the ones who stayed with the equipment, "and the portion of the men" who went to war. In Breishis Raboh.

To his allies. To his friends.

Where Dovid [and his men] had gone. For they would hide him from Shaul.