Musnad Ahmad 8:69

Hassan narrated to us, Hammad ibn Salamah narrated to us, from Qatadah, from ‘Umar ibn Sa‘d ibn Malik, from Sa‘d, from the Messenger of Allah, may Allah bless him and grant him peace, who said: "For the interior of one of you to be filled with pus until it consumes him is better than for it to be filled with poetry."