Rulings for the waiting period
What is the ruling for a man is married to four wives simultaneously and divorces one of them with a revocable divorce on the first day of the month? Is it permissible for him to take another wife other than the one he divorced? Does a man observe a waiting period after divorce or must he wait until the waiting period of the wife he divorced ends before remarrying so as not to violate the juristic rule which states that it is impermissible for a man to combine between five wives in marriage?
It is impermissible for a man who is married to four wives to take a fifth except if he divorces one of them and her waiting period ends so as not to combine between five or more wives in marriage.
Combining wives during a divorcee's waiting period is tantamount to combining them in marriage. This is because the waiting period after a divorce entails the same rulings in respect to conjugal relations.
It is impermissible for a man to take a fifth wife when one of his other four wives is still in her waiting period since he would then be combining between five wives.
The answer to the question is known from the above and Allah Almighty knows best.