Musnad Ahmad 27:924

Ya'qub narrated to us, I heard my father narrating, from Yazid—meaning Ibn al-Had—from 'Umar ibn 'Abdullah, that he narrated to him that 'Abdullah ibn 'Umar met some people who had come out from Marwan. He said, "Where did these people come from?" They said, "We came out from the presence of the Amir, Marwan." He said, "And every truth you saw, did you speak of it and support it? And every evil you saw, did you denounce it and reject it to him?" They said, "No, by Allah. Rather, he says something that should be denounced, and we say, 'You have spoken correctly, may Allah rectify you.' But when we leave his presence, we say, 'May Allah fight him, how oppressive and wicked he is!'" 'Abdullah said, "In the time of the Messenger of Allah, peace and blessings of Allah be upon him, we used to consider this hypocrisy for whoever was like this."