Musnad Ahmad 27:526

Ishaq ibn Sulayman narrated to us, I heard Hanzalah ibn Abi Sufyan al-Jumahi, I heard Salim ibn Abdullah saying: I heard Abdullah ibn Umar saying: I heard the Messenger of Allah, may Allah bless him and grant him peace, saying: "For the interior of one of you to be filled with pus is better for him than for it to be filled with poetry."