2 Samuel 3:6 (BSB)

During the war between the house of Saul and the house of David, Abner had continued to strengthen his position in the house of Saul.

From 2 Samuel 3. Also in the ESV.

Commentary on 2 Samuel 3:6

• Matthew Henry (Presbyterian), Matthew Henry's Complete Commentary on 2 Samuel 3:1-6: Here is, I. The struggle that David had with the house of Saul before his settlement in the throne was completed, Sa2 3:1. 1. Both sides contested. Saul's house, though beheaded and diminished, would not fall tamely. It is not strange between them, but one would wonder it should be a long war, when David's house had right on its side, and therefore God on...
• John Gill (Reformed Baptist), Exposition of the Old and New Testaments on 2 Samuel 3:6: And it came to pass, while there was war between the house of Saul and the house of David,.... As long as that continued, as it did until the following quarrel happened between Ishbosheth and Abner: that Abner made himself strong for the house of Saul; or was strongly in the interest of that house, and used his utmost endeavours to support and confirm it.
• Jamieson-Fausset-Brown (Reformed), Commentary Critical and Explanatory on the Whole Bible on 2 Samuel 3:6: ABNER REVOLTS TO DAVID. (Sa2 3:6-12) Abner made himself strong for the house of Saul--In the East, the wives and concubines of a king are the property of his successor to this extent, that for a private person to aspire to marry one of them would be considered a virtual advance of pretensions to the crown (see Kg1 2:17).
• Adam Clarke (Methodist), Clarke's Commentary on the Bible on 2 Samuel 3:6: Abner made himself strong - This strengthening of himself, and going in to the late king's concubine, were most evident proofs that he wished to seize upon the government. See Kg1 2:21, Kg1 2:22; Kg1 12:8; Kg1 16:21.