Why did king David give Abner his first wife Michal?

According to the biblical account, King David did not give Abner his first wife Michal. Michal was initially married to King Saul's son, Ish-Bosheth, and remained married to him until David became the sole king of Israel. Later, David tookMichal back to his palace, but there is no mention in the Bible of him giving her to Abner.