Abu al-Zubayr (may Allah have mercy on him) states that he heard Sayyiduna Jabir bin Abdullah (may Allah be pleased with him) being asked about a woman who had taken upon herself an Umrah in a specified month; the month passed except for one night, and then she began menstruating. He said: She should set out and make the talbiyah for Umrah, then wait until she becomes pure; after becoming pure she should perform tawaf of the House of Allah, then pray.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب النذور / 20145