Charles Ellicott Commentary 1 Samuel 26:5

"And David arose, and came to the place where Saul had encamped; and David beheld the place where Saul lay, and Abner the son of Ner, the captain of his host: and Saul lay within the place of the wagons, and the people were encamped round about him." — 1 Samuel 26:5 (ASV)

And David arose. —Immediately after the scouts informed him of Saul's purpose and the nearness of the royal army, David seems to have resolved to undertake that night adventure which resulted in the episode told in this twenty-sixth chapter.

In the trench. —The English Version (Margin) has, “in the midst of his carriages”; Keil renders it, “by the wagon rampart”; The Septuagint translates the Hebrew word as “covered chariots.” The meaning is, no doubt, that the king lay down within the barricade or rampart formed by the baggage wagons.