Musnad Ahmad 30:1965

Aswad narrated to us, Sharik narrated to us, from al-A'mash, from Abu Salih, from Abu Hurairah, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "For the inside of one of you to be filled with pus that consumes him is better for him than for it to be filled with poetry."