كتاب الحج
15  
The Book of Pilgrimage
(35)
Chapter: The number of Umrahs performed by the prophet (saws) and when he performed them
(35)
باب بَيَانِ عَدَدِ عُمَرِ النَّبِيِّ صلى الله عليه وسلم وَزَمَانِهِنَّ ‏
Sahih Muslim 1253 a

Qatada said:

I asked Anas (Allah be pleased with him) as to how many Pilgrimages had been performed by Allah's Messenger (ﷺ), and he replied: One Hajj and four `Umras were performed by him. The rest of the hadith is the same.
حَدَّثَنَا مُحَمَّدُ بْنُ الْمُثَنَّى، حَدَّثَنِي عَبْدُ الصَّمَدِ، حَدَّثَنَا هَمَّامٌ، حَدَّثَنَا قَتَادَةُ، قَالَ سَأَلْتُ أَنَسًا كَمْ حَجَّ رَسُولُ اللَّهِ صلى الله عليه وسلم قَالَ حَجَّةً وَاحِدَةً وَاعْتَمَرَ أَرْبَعَ عُمَرٍ ‏.‏ ثُمَّ ذَكَرَ بِمِثْلِ حَدِيثِ هَدَّابٍ ‏.‏
Reference : Sahih Muslim 1253a
In-book reference : Book 15, Hadith 240
USC-MSA web (English) reference : Book 7, Hadith 2880
  (deprecated numbering scheme)