"Narrated Aisha: The wife of Rifaa Al-Qurazi came to Allah's Apostle and said, 'O Allah's Apostle, Rifaa divorced me irrevocably. After him I married Abdur-Rahman bin Az-Zubair Al-Qurazi who proved to be impotent.'
Allah's Apostle said to her, 'Perhaps you want to return to Rifaa? Nay (You cannot return to Rifaa ) until you and Abdur-Rahman (the impotent man) engage in sexual intercourse! '" Vol. 7:186
When a husband pronounced his wife divorce three times “thrice divorced”
and wants to remarry her, he cannot do it lawfully until he pays
another man “Al Mohalil”(which means the legalizer) who marries this
thrice divorced woman and (had sexual intercourse or consummating the
marriage with her) and then dismisses her so that she may lawfully marry
her former husband.