كتاب الإيمان
1  
The Book of Faith
(12)
Chapter: Clarifying the number of branches of faith, the best and the least of them, the virtue of modesty (Al-Haya') and the fact that it is part of faith
(12)
باب بَيَانِ عَدَدِ شُعَبِ الْإِيمَانِ وَأَفْضَلِهَا وَأَدْنَاهَا وَفَضِيلَةِ الْحَيَاءِ وَكَوْنِهِ مِنْ الْإِيمَانِ
Sahih Muslim 36 b

Zuhri has narrated this hadith with the addition of these words:

He (the Holy Prophet) happened to pass by a mass of Ansar who was instructing his brother (about modesty).
حَدَّثَنَا عَبْدُ بْنُ حُمَيْدٍ، حَدَّثَنَا عَبْدُ الرَّزَّاقِ، أَخْبَرَنَا مَعْمَرٌ، عَنِ الزُّهْرِيِّ، بِهَذَا الإِسْنَادِ وَقَالَ مَرَّ بِرَجُلٍ مِنَ الأَنْصَارِ يَعِظُ أَخَاهُ ‏.‏
Reference : Sahih Muslim 36b
In-book reference : Book 1, Hadith 62
USC-MSA web (English) reference : Book 1, Hadith 58
  (deprecated numbering scheme)