Sa'id bin al-Musayyib (may Allah have mercy on him) said: It is an error on the part of Ibn Abbas (may Allah be pleased with them both) that the Prophet (peace and blessings be upon him) married Maymunah (may Allah be pleased with her) while in the state of ihram.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب النكاح / 14209