Notes on the Bible, by Albert Barnes, [1834], at sacred-texts.com
The incident related in this chapter of the meeting between Saul and David bears a strong general resemblance to that recorded in 1 Sam. 24, and is of a nature unlikely to have occurred more than once. Existing discrepancies are explained by the supposition that one narrative relates fully some incidents on which the other is silent. On the whole the most probable conclusion is that the two narratives relate to one and the same event. (Compare the two narratives of the Creation, Gen. 1; Gen 2:4 ff; the two narratives of David's war, 2 Sam. 8; and 2 Sam. 10; and those of the death of Ahaziah, Kg2 9:27 ff; and Ch2 22:9.)
Ahimelech the Hittite - Only mentioned here. Uriah was also a Hittite.
Abishai - He was son of Zeruiah, David's sister, but probably about the same age as David. He because very famous as a warrior Sa2 23:18, but was implicated with his brother Joab in the murder of Abner in retaliation for the death of their brother Asahel Sa2 3:30.
This incidental testimony to Abner's great eminence as a warrior is fully borne out by David's dirge at Abner's death Sa2 3:31-34, Sa2 3:38, as well as by his whole history. At the same time David's bantering tone in regard to Abner, coupled with what he says in Sa1 26:19, makes it proable that David attributed Saul's persecution of him in some degree to Abner. Abner would be likely to dread a rival in the young conqueror of Judah (compare Sa2 2:8).
If the Lord have stirred thee up - The meaning is clear from the preceding history. "An evil spirit from God troubling him" was the beginning of the persecution. And this evil spirit was sent in punishment of Saul's sin Sa1 16:1, Sa1 16:14. If the continued persecution was merely the consequence of this evil spirit continuing to vex Saul, David advises Saul to seek God's pardon, and, as a consequence, the removal of the evil spirit, by offering a sacrifice. But if the persecution was the consequence of the false accusations of slanderers, then "cursed" be his enemies who, by their actions, drove David out from the only land where Yahweh was worshipped, and forced him to take refuge in the country of pagan and idolaters (compare Deu 4:27; Deu 28:36).