Nafi' (may Allah have mercy on him) says that a man asked Sayyiduna Abdullah bin Umar (may Allah be pleased with them both): I have given my wife three divorces while she was menstruating. He said: You have disobeyed your Lord and separated from your wife.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الخلع والطلاق / 14969