Musannaf Ibn Abi Shayba 36:521

Yazid ibn Harun narrated to us, from Abd al-Aziz ibn Abd Allah ibn Abi Salamah, from Abd al-Rahman ibn Abi Awn, from al-Qasim ibn Muhammad, from Aisha, that she used to say: The Messenger of Allah (peace and blessings of Allah be upon him) passed away, and there descended upon Abu Bakr that which, had it descended upon the mountains, would have crushed them. Hypocrisy reared its head in Medina, and the Arabs apostatized. By Allah, they did not differ on a single point except that my father flew to its share and its defense in Islam. And she used to say, along with this: Whoever saw Umar ibn al-Khattab knew that he was created as a source of sufficiency for Islam. By Allah, he was skillful, unique in his character, and he had prepared for matters their equals.