Musnad Ahmad 27:1869

'Abd al-Razzaq narrated to us, Ibn Jurayj and Rawh informed us, they said: Ibn Jurayj narrated to us, Ibn Tawus informed me, from his father, that he heard Ibn 'Umar being asked about a man who divorced his wife while she was menstruating. He said: "Do you know 'Abdullah ibn 'Umar?" He said: "Yes." He said: "For he divorced his wife while she was menstruating. So 'Umar went to the Prophet, may Allah bless him and grant him peace, and informed him of the news. So he commanded him to take her back." He said: "And I did not hear him add anything to that." Rawh said once: "To return her."