Musannaf Ibn Abi Shayba 33:936

Abu Usama narrated to us, from Awf, from Abu al-Minhal, who said: Safwan ibn Muhriz narrated to me, saying: Jundub said: The likeness of the one who preaches to others while forgetting himself is like a lamp that gives light to others while burning itself. Let one of you look carefully at what he puts into his stomach, for when a beast dies, the first part of it to burst is its belly. And let one of you fear that a handful of a Muslim's blood might come between him and Paradise.