Muwatta Malik, Book 47, Hadith 1645 (In-Book) ⓘ

Yahya related to me from Malik from Ibn Shihab from Salim ibn Abdullah from Abdullah ibn Umar that the Messenger of Allah, may Allah bless him and grant him peace, passed by a man who was chiding his brother about modesty. The Messenger of Allah, may Allah bless him and grant him peace, said, "Leave him. Modesty is part of iman."

وَحَدَّثَنِي عَنْ مَالِكٍ، عَنِ ابْنِ شِهَابٍ، عَنْ سَالِمِ بْنِ عَبْدِ اللَّهِ، عَنْ عَبْدِ اللَّهِ بْنِ عُمَرَ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم مَرَّ عَلَى رَجُلٍ وَهُوَ يَعِظُ أَخَاهُ فِي الْحَيَاءِ فَقَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم ‏ "‏ دَعْهُ فَإِنَّ الْحَيَاءَ مِنَ الإِيمَانِ ‏" ‏ ‏.‏