Must a man who embraces Islam while married to more than four women proceed to choose only four?
Chapter on Marriage of Polytheists
Al-Mughni
Book of Marriage
Primary text
He is obligated to choose four or fewer and separate from the rest, or separate from all of them, because the command given to Ghaylan and Qays implies obligation. Since a Muslim is not permitted to remain married to more than four, if he refuses to choose, he shall be compelled through imprisonment and disciplinary action until he makes a choice, as this is a fulfillable right upon him which he is refusing.
Supporting text
The magistrate (Hakim) is not authorized to make the choice on his behalf, unlike the situation of a man who refuses to pronounce divorce (Muli), because the right here belongs to an indefinite party, and the wives only become determined through his personal choice and desire, which the magistrate cannot ascertain. Furthermore, if the man becomes insane (junna) until his reason returns, he is then compelled to choose, and he owes maintenance (Nafaqah) to all of them until the choice is made, as they are effectively held in confinement under his status as wives, and whichever he chooses becomes valid.