Imam al-Shafi'i (may Allah have mercy on him) said: "(Let him give one divorce) so that he retains the right to take back the woman with whom the marriage has been consummated, and, in the case of one with whom it has not been consummated, he can (again) be a suitor proposing to her; and whenever she is married (to him again), two divorces will remain for him over her.
And it is not unlawful for him to give two or three divorces, because Allah Almighty, glorified be His praise, has made divorce permissible for those entitled to it, and what He has made permissible is not forbidden to those entitled to it; and (also) because the Messenger of Allah (peace and blessings be upon him) taught Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) the (correct) time for divorce, and if some numbers of divorce were permissible and some forbidden, he (peace and blessings be upon him), Allah willing, would certainly have taught him that as well."
Salim narrates from Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) that he divorced his wife while she was menstruating, and Sayyiduna Umar (may Allah be pleased with him) told the Prophet (peace and blessings be upon him), and he (peace and blessings be upon him) said: "Order him to take her back, then to divorce her when she is pure or pregnant."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الخلع والطلاق / 14934