Musnad Abu Ya'la al-Mawsili 2:39

Uthman ibn Abi Shaybah narrated to us, Abdullah ibn Idris narrated to us, from Muhammad ibn Ishaq, from al-Zuhri, from Ubayd Allah ibn Abdullah ibn Abi Thawr, from Ibn Abbas, who said: I said to Umar ibn al-Khattab, "O Commander of the Faithful, who are the two women who supported one another against the Messenger of Allah, may Allah bless him and grant him peace?" He said, "Aisha and Hafsa."