It is Not Permissible Until She Has Married Another

Question :

A man divorced his wife for the third time and four years passed. Now he wishes to take her back with a new contract and a new dowry, without anyone to make her permissible for him (i.e. another husband). Is this permissible?

Answer:

If a man has clearly divorced his wife three times, she is not permissible for him until she marries another man. There is no difference between a short period of time (since the divorce) and a long period. Thus, if they both agree to him taking her back one hour after the divorce or years after it, she is not permissible for him because it is an irrevocable divorce.

So another man must marry her of his own free will, not for the purpose of making her permissible for her first husband. Then if the second husband divorces her of his own free will, there is no sin upon them if they reunite with a new contract and a new dowry. However, if the divorce was revocable, such as the first or the second, then she is permissible for him without a marriage contract, as long as she is in her waiting period. But after the waiting period, she must agree, the contract must be renewed, and another dowry paid. And Allah knows best.

Source:
Ibn Jibreen
Fatawa Islamiyah, Vol. 6 Page 73