Nafi' narrates from Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) that he gave his wife one divorce while she was menstruating, so the Messenger of Allah (peace and blessings be upon him) ordered him to take her back: "then keep her until she becomes pure, then after another menstruation give her time until she becomes pure; then if he intends to divorce her, let him divorce her in the state of purity before having intercourse with her. This is the waiting period for which Allah, the Lord of Might, has commanded that women be divorced." And when Sayyiduna Ibn Umar (may Allah be pleased with them both) was asked about this, he would say: If you have given your wife three divorces, she has become unlawful for you until she marries another husband, and you have disobeyed the command of Allah, the Lord of Might, that He gave regarding divorcing women.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الخلع والطلاق / 14940