Musannaf Ibn Abi Shayba 30:151

Muhammad ibn Bishr narrated to us, he said: Zakariya ibn Abi Za'idah narrated to us, from 'Atiyyah, from Abu Sa'id, that the Prophet (peace and blessings of Allah be upon him) said: "Indeed, I have a basin (Hawd) whose length is what is between the Ka'bah and Bayt al-Maqdis. It is whiter than milk, and its vessels are the number of the stars. And I am the prophet with the most followers on the Day of Resurrection."