Musnad Ahmad 8:97

Bahz narrated to us, Shu'bah narrated to us, Qatadah narrated to us, from Yunus ibn Jubayr, from Muhammad ibn Sa'd ibn Abi Waqqas, from his father, that the Messenger of Allah (peace and blessings of Allah be upon him) said: "For the interior of one of you to be filled with pus and blood is better for him than for it to be filled with poetry."