1 Samuel 30:6-10

And David was greatly distressed; for the people spake of stoning him, because the soul of all the people was grieved, every man for his sons and for his daughters: but David encouraged himself in the LORD his God.

And David said to Abiathar the priest, Ahimelech’s son, I pray thee, bring me hither the ephod. And Abiathar brought thither the ephod to David.

And David enquired at the LORD, saying, Shall I pursue after this troop? shall I overtake them? And he answered him, Pursue: for thou shalt surely overtake them, and without fail recover all.

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.

But David pursued, he and four hundred men: for two hundred abode behind, which were so faint that they could not go over the brook Besor.