Musnad Ahmad 1007:75

'Abd al-Razzaq narrated to us, Ma'mar narrated to us, 'Abd Allah ibn Muhammad ibn 'Aqil—meaning Ibn Abi Talib—informed me, he said: Mu'awiyah came to Medina, and Abu Qatadah met him. He said: "Verily, the Messenger of Allah (ﷺ) said: 'You will encounter after me favoritism (in the distribution of wealth and affairs).'" He (Mu'awiyah) said: "Then what did he command you?" He (Abu Qatadah) said: "He commanded us to be patient." He (Mu'awiyah) said: "Then be patient."