سنن ابن ماجه

It was narrated from Abu Sa’eed Al-Khudri that the Prophet (ﷺ) said: “I have a Cistern, (as large as the distance) between the Ka’bah and Baitul-Maqdis (Jerusalem). (It is) whiter than milk, and its vessels are the number of the stars. I will be the Prophet (ﷺ) with the most followers on the Day of Resurrection.”