Musnad Ahmad 27:1666

Ubaydah ibn Humayd narrated to us, from Mansur ibn al-Mu'tamir, from Mujahid, who said: I and Urwah ibn al-Zubayr entered the mosque, and there we were with Abdullah ibn Umar, so we sat with him. He said: Then there were men praying the Duha (forenoon) prayer, so we said: "O Abu Abd al-Rahman, what is this prayer?" He said: "An innovation." We said to him: "How many times did the Messenger of Allah, peace and blessings of Allah be upon him, perform Umrah?" He said: "Four times, one of them in Rajab." He said: So we were too shy to refute him. He said: Then we heard the rustling of the Mother of the Believers, Aisha. Urwah ibn al-Zubayr said to her: "O Mother of the Believers, do you not hear what Abu Abd al-Rahman is saying? He says: 'The Messenger of Allah, peace and blessings of Allah be upon him, performed Umrah four times, one of them in Rajab.'" She said: "May Allah have mercy on Abu Abd al-Rahman. Verily, he did not perform any Umrah except that he was a witness to it, and he did not perform any Umrah in Rajab."