Musannaf Ibn Abi Shayba 27:485

Humaid ibn Abd al-Rahman narrated to us, from his father, from Abu Ishaq, from his grandmother Maymunah, who said: When the division occurred, it was said to Maymunah bint al-Harith, "O Mother of the Believers!" She said, "You must follow the son of Abu Talib, for by Allah, he did not go astray, nor was anyone led astray by him."