Musnad Ahmad 30:1758

Ishaq narrated to us, Malik informed us, from Suhayl, from his father, from Abu Hurayrah, that a guest stayed with the Messenger of Allah, may Allah bless him and grant him peace, and he was a disbeliever. The Messenger of Allah, may Allah bless him and grant him peace, ordered a sheep, so it was milked, and the disbeliever drank its milk. Then another, and he drank it, then another, and he drank it, until he drank the milk of seven sheep. Then, he woke up in the morning and embraced Islam. The Messenger of Allah, may Allah bless him and grant him peace, ordered a sheep for him, and he drank its milk, then he ordered another, but he could not finish it. The Messenger of Allah, may Allah bless him and grant him peace, said: "The believer drinks in one intestine, and the disbeliever drinks in seven intestines."