Musannaf Ibn Abi Shayba 33:348

Shababa bin Sawwar narrated to us, he said: Shu'bah narrated to us, from al-A'mash, from 'Abdullah bin Murrah, from Abu Kanf, that a man saw a dream and began to relate it to Ibn Mas'ud, and he (the man) was fat. Ibn Mas'ud said: "I truly dislike for the reciter (of the Quran) to be fat." Al-A'mash said: So I mentioned that to Ibrahim, and he said: "A fat person is forgetful of the Quran."