Sahih al-Bukhari 6581
Narrated Anas bin Malik:
The Prophet (ﷺ) said: "While I was walking in Paradise (on the night of Mi'raj), I saw a river, on the two 
banks of which there were tents made of hollow pearls. I asked, "What is this, O Gabriel?' He said, 
'That is the Kauthar which Your Lord has given to you.' Behold! Its scent or its mud was sharp 
smelling musk!" (The sub-narrator, Hudba is in doubt as to the correct expression. )
حَدَّثَنَا أَبُو الْوَلِيدِ، حَدَّثَنَا هَمَّامٌ، عَنْ قَتَادَةَ، عَنْ أَنَسٍ، عَنِ النَّبِيِّ صلى الله عليه وسلم‏.‏ وَحَدَّثَنَا هُدْبَةُ بْنُ خَالِدٍ، حَدَّثَنَا هَمَّامٌ، حَدَّثَنَا قَتَادَةُ، حَدَّثَنَا أَنَسُ بْنُ مَالِكٍ، عَنِ النَّبِيِّ صلى الله عليه وسلم قَالَ ‏
"‏ بَيْنَمَا أَنَا أَسِيرُ فِي الْجَنَّةِ إِذَا أَنَا بِنَهَرٍ حَافَتَاهُ قِبَابُ الدُّرِّ الْمُجَوَّفِ قُلْتُ مَا هَذَا يَا جِبْرِيلُ قَالَ هَذَا الْكَوْثَرُ الَّذِي أَعْطَاكَ رَبُّكَ‏.‏ فَإِذَا طِينُهُ ـ أَوْ طِيبُهُ ـ مِسْكٌ أَذْفَرُ ‏"‏‏.‏ شَكَّ هُدْبَةُ‏.‏