كتاب الإيمان
1  
The Book of Faith
(85)
Chapter: Regarding the saying of the Prophet (saws): "I will be the first of the people to intercede concerning Paradise, and I will be the Prophet with the Greatest Number of Followers."
(85)
باب فِي قَوْلِ النَّبِيِّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ: «أَنَا أَوَّلُ النَّاسِ يَشْفَعُ فِي الْجَنَّةِ وَأَنَا أَكْثَرُ الأَنْبِيَاءِ تَبَعًا»
Sahih Muslim 196 c

Anas b. Malik said:

The Apostle of Allah (ﷺ) said: I would be the first intercessor in the Paradise and no apostle amongst the apostles has been testified (by such a large number of people) as I have been testified. And verily there woald be an apostle among the apostles who would be testified to by only one man from his people.
وَحَدَّثَنَا أَبُو بَكْرِ بْنُ أَبِي شَيْبَةَ، حَدَّثَنَا حُسَيْنُ بْنُ عَلِيٍّ، عَنْ زَائِدَةَ، عَنِ الْمُخْتَارِ بْنِ فُلْفُلٍ، قَالَ قَالَ أَنَسُ بْنُ مَالِكٍ قَالَ النَّبِيُّ صلى الله عليه وسلم ‏ "‏ أَنَا أَوَّلُ شَفِيعٍ فِي الْجَنَّةِ لَمْ يُصَدَّقْ نَبِيٌّ مِنَ الأَنْبِيَاءِ مَا صُدِّقْتُ وَإِنَّ مِنَ الأَنْبِيَاءِ نَبِيًّا مَا يُصَدِّقُهُ مِنْ أُمَّتِهِ إِلاَّ رَجُلٌ وَاحِدٌ ‏"‏ ‏.‏
Reference : Sahih Muslim 196c
In-book reference : Book 1, Hadith 391
USC-MSA web (English) reference : Book 1, Hadith 383
  (deprecated numbering scheme)