From Sahih Muslim (Hadith 5096):
Rafi' b. Khadij reported that he said:Allah's Messenger, we are going to encounter the enemy tomorrow. and we do not have large knives with us. The rest of the hadith is the same, but no mention is made of this:" The people hastened and they boiled (flesh) in the earthen pots. He (the Holy Prophet), cammanded and these were turned over and the narrator narrated the whole event
Reference: Muslim 5096