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 Sayyidah Maymunah (may Allah be pleased with her) while he (peace and blessings be upon him) was in the state of ihram.
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 11294