It is narrated from Sayyiduna Ibn Abbas (may Allah be pleased with them both) that the Messenger of Allah (peace and blessings be upon him) married Maymunah (may Allah be pleased with her) while in the state of ihram. Sa'id (may Allah have mercy on him) said: Ibn Abbas (may Allah be pleased with them both) was mistaken, even though she was his maternal aunt; the Messenger of Allah (peace and blessings be upon him) married her only after he had come out of ihram.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب النكاح / 14210