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 ‏.‏