Musannaf Ibn Abi Shayba 33:1285

Affan narrated to us, he said: Abd al-Rahman narrated to us, from Abd al-Wahid ibn Ziyad, he said: Abd Allah ibn al-Rabi’ ibn Khuthaym narrated to us, he said: Abu Ubaydah ibn Abd Allah narrated to us, he said: When al-Rabi’ ibn Khuthaym would enter upon Abd Allah, he would not have permission [to enter] on that day until each one of them had finished with the other. He said: And Abd Allah said to him: "O Abu Yazid, if the Messenger of Allah, may Allah bless him and grant him peace, had seen you, he would have loved you. And I have never seen you except that I remembered the humble ones (al-mukhbitin)."