John Gill Commentary 1 Samuel 26

And the Ziphites came to Saul to Gibeah
Of Benjamin, called sometimes Gibeah of Saul, because it was the place of his birth and residence.

Here Saul has returned after his last interview with David; whether, notwithstanding what has passed between him and David, he has privately encouraged the Ziphites to watch David, and give him information of him where he was, and when it was a proper opportunity to seize him; or whether the Ziphites were so officious as of themselves to acquaint him with it, is not certain; the latter is probable, since having attempted to betray David, they might fear, that should he come to the throne, he would remember it, and therefore they might be desirous of having him cut off by the hand of Saul:

saying, does not David hide himself in the hill of Hachilah, [which is]
before Jeshimon ?

the same place where he was when the Ziphites before gave information of him, (1 Samuel 23:10) ; here he might choose to be, supposing that the Ziphites now would not meditate anything against him, since Saul had declared he would be king after him, and had made him swear that he would not cut off his posterity; and as he thought it his wisdom to provide against the worst, knowing the inconstancy of Saul, he might judge this the most proper place of safety, and from where he could, on occasion, easily retreat into the wilderness; and it may be also, because it was near to Abigail's estate and possessions, which were now a good resource for him.

Then Saul arose
Immediately, glad of an opportunity to seize on David, having the same disposition towards him as ever; and perhaps had repented he had not laid hold on him when he followed him out of the cave:

and went down to the wilderness of Ziph :
or towards it:

having three thousand chosen men of Israel ;
young men, so called, because usually chosen for business, and for war particularly, rather than old men; the same number he took with him when he sought him at Engedi, (1 Samuel 24:2) ;

to seek David in the wilderness of Ziph ;
where or whereabouts he was informed by the Ziphites he was.

And Saul pitched in the hill of Hachilah, which [is] before
Jeshimon, by the way
To the wilderness; the very same place where the Ziphites suggested David was:

but David abode in the wilderness ;
not in the hill of Hachilah, but in the wilderness of Ziph itself:

and he saw that Saul came after him into the wilderness ;
he understood, by some information he had, that Saul had set out from Gibeah, and was coming to seek for him in the wilderness of Ziph; perhaps Jonathan had given him intelligence; however, he was not quite certain, as appears by what follows.

David therefore sent out spies
To observe if he was coming or come, and where he was, that he might not be surprised by him; for though David knew the Lord was and would be his protection, he thought proper to be upon his guard, and to make use of means for his safety:

and understood that Saul was come in very deed ;
that he was most certainly come, and come to some certain place; which he himself went to reconnoitre, as in (1 Samuel 26:5) .

And David arose, and came to the place where Saul had pitched ,
&c.] Came near it, within sight of it; so that he could take a view of it with his naked eye, and observe where and in what manner he was encamped:

and David beheld the place where Saul lay, and Abner the son of Ner ,
the captain of his host ;
where he and his general had their quarters in the camp:

and Saul lay in the trench ;
or circuit; not in the foss or ditch thrown up, in which an army sometimes lies entrenched; but this is to be understood either of the camp itself, so called, as Ben Gersom, Abarbinel, and Ben Melech think, because it lay in a circular form, that all comers to it on every side might be seen; or else a sort of fortress all around the camp, made of carriages joined together; and as the word signifies a carriage, cart or chariot, it may design the chariot in which Saul slept, as kings have been used to do when not in their houses; and to this the Septuagint agrees, which uses a word that Procopius Gazaeus says signifies one kind of a chariot, and is used of a chariot drawn by mules, in the Greek version of (Isaiah 66:20) ; Grotius observes, kings used to sleep in chariots where there were no houses; (See Gill on 1 Samuel 17:20); though he rather seems to have slept, "sub die", in the open air:

and the people pitched round about him ;
both for the sake of honour, and for his greater security; this shows it could not be the loss he laid in, for then they could not pitch around him.