Nafi' narrates from Ibn Umar (may Allah be pleased with them both) that a man came to Sayyiduna Umar (may Allah be pleased with him) and said: "I have given my wife a battah (irrevocable) divorce while she was menstruating." He said: "You have disobeyed your Lord and separated from your wife." The man said that the Messenger of Allah (peace and blessings be upon him) had ordered Ibn Umar (may Allah be pleased with them both), when he separated from his wife, to take her back. Sayyiduna Umar (may Allah be pleased with him) said: "The Messenger of Allah (peace and blessings be upon him) ordered him to take her back because a divorce remained for him, but no divorce remains for you by which you could take your wife back."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الخلع والطلاق / 14956