Musnad Ahmad 30:1534

Aswad ibn Amir narrated to us, he said: Sharik narrated to us, from al-A'mash, from Abu Salih, from Abu Hurairah, he said: 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 that consumes him is better for him than for it to be filled with poetry."