Albert Barnes Commentary 2 Samuel 3:21

"And Abner said unto David, I will arise and go, and will gather all Israel unto my lord the king, that they may make a covenant with thee, and that thou mayest reign over all that thy soul desireth. And David sent Abner away; and he went in peace." — 2 Samuel 3:21 (ASV)

Abner repeats the offer (2 Samuel 3:12), and with the condition for Michal’s return now fulfilled (2 Samuel 3:13), David accepts it. The alliance between them was then solemnly ratified at David’s table, amidst the rites of hospitality.