Ibn Hibban

Sayyiduna Abu Hurairah (may Allah be pleased with him) narrates: A disbeliever came as a guest to the Prophet Muhammad (peace and blessings be upon him). By the order of the Prophet (peace be upon him), milk from a goat was milked for him. He drank its milk, then milk from a second goat was milked and he drank that as well, then milk from another was milked and he drank that too, until he drank the milk of seven goats. The next day, he became a Muslim. By the order of the Prophet (peace be upon him), milk from a goat was milked for him and he drank it, then by the order of the Prophet (peace be upon him), milk from a second goat was milked but he could not finish it completely. The Prophet (peace be upon him) said: "Indeed, a believer drinks in one intestine, and a disbeliever drinks in seven intestines."