Sahih Muslim
The Book Pertaining to the Excellent Qualities of the Holy Prophet (may Peace be upon them) and His Companions (Kitab Al-Fadail)
Book Number: 030 / Hadith Number: 5696
Ibn 'Umar reported Allah's Messenger (may peace be upon him) as saying: There is before you a Cistern and the distance between its two sides is as it is between Jarba' and Adhruh.