ENOfficial
It was narrated from Salim that his father said: "The Messenger of Allah (ﷺ) said heard a man urging his brother to be modest. He said: 'Indeed modesty is a branch of faith.'"
Source: sunnah.com
Other translations
Arabic
حَدَّثَنَا سَهْلُ بْنُ أَبِي سَهْلٍ، وَمُحَمَّدُ بْنُ عَبْدِ اللَّهِ بْنِ يَزِيدَ، قَالاَ حَدَّثَنَا سُفْيَانُ، عَنِ الزُّهْرِيِّ، عَنْ سَالِمٍ، عَنْ أَبِيهِ، قَالَ سَمِعَ النَّبِيُّ ـ صلى الله عليه وسلم ـ رَجُلاً يَعِظُ أَخَاهُ فِي الْحَيَاءِ فَقَالَ " إِنَّ الْحَيَاءَ شُعْبَةٌ مِنَ الإِيمَانِ " .
sunnah.com