Sahih Muslim 5966
The Book of Virtues
حَدَّثَنِي أَحْمَدُ بْنُ عَبْدِ اللَّهِ بْنِ يُونُسَ، حَدَّثَنَا زَائِدَةُ، حَدَّثَنَا عَبْدُ الْمَلِكِ بْنُ عُمَيْرٍ، قَالَ سَمِعْتُ جُنْدَبًا، يَقُولُ سَمِعْتُ النَّبِيَّ صلى الله عليه وسلم يَقُولُ " أَنَا فَرَطُكُمْ، عَلَى الْحَوْضِ " .
Jundab reported:I heard Allah's Messenger (ﷺ) as saying: I shall be there at the Cistern before you
Text from the public-domain hadith-api dataset. Numbering follows that dataset and can differ by a few from some printed editions — check the wording, not only the number.