Matthew Poole and continuators on 2 Samuel 3:6

6 ¶ And it came to pass while there was war between the house of Saul, and the house of David, that Abner made himself strong for the house of Saul .

He used all his endeavours to support Saul's House. Which is mentioned, to shew the reason of his deep resentment of the following aspersion. Or, he strengthned himself in the House of Saul, i. e. he so managed all Affairs, as to get all the riches and power into his own hands: which made Ishbosheth suspect that he aimed at the Kingdom, and sought to Marry the Kings Concubine in order to it, as the manner was. See 2 Sam. 12. 8. and 16. 21. and 1 King. 1. 17.