Sahih al-Bukhari, Hadith 6591 ⓘ
Narrated Haritha bin Wahb: I heard the Prophet mentioning the Lake-Fount (Al-Kauthar), saying, "(The width of the Lake-Fount) is equal to the distance between Medina and Sana' (capital of Yemen)."
حَدَّثَنَا عَلِيُّ بْنُ عَبْدِ اللَّهِ، حَدَّثَنَا حَرَمِيُّ بْنُ عُمَارَةَ، حَدَّثَنَا شُعْبَةُ، عَنْ مَعْبَدِ بْنِ خَالِدٍ، أَنَّهُ سَمِعَ حَارِثَةَ بْنَ وَهْبٍ، يَقُولُ سَمِعْتُ النَّبِيَّ صلى الله عليه وسلم وَذَكَرَ الْحَوْضَ فَقَالَ " كَمَا بَيْنَ الْمَدِينَةِ وَصَنْعَاءَ " .
also referenced under: Book 81, Hadith 179 (In-Book) & Volume 8, Book 76, Hadith 591 (USC-MSA)