From Sahih Muslim (Hadith 3453):
Yazid b. al-Asamm reported:Maimuna daughter of al-Harith narrated to me that Allah's Messenger (ﷺ) married her and he was not in the state of Ihram. And she (Maimuna) was my mother's sister and that of Ibn 'Abbas (Allah be pleased with them)
Reference: Muslim 3453