Sahih Muslim Book 009, Hadith Number 3488.
Chapter: It is forbidden to divorce the woman during her menses.
Ibn Tawus narrated on the authority of his father that Ibn 'Umar (Allah be pleased with them) was asked about the person who divorced his wife in the state of menses, whereupon he said: Do you know 'Abdullah b. Umar? He said: Yes. He said: It was he who divorced his wife in the state of menses and 'Umar went to Allah's Apostle (may peace be upon him) and gave him this information. and he commanded him that he should take her back; and he (Abu Tawus) said: I did not hear any addition to this (hadith) from my father.