The Messenger of Allah ﷺ passed by a man who was admonishing his brother about modesty. The Messenger of Allah ﷺ said, "Modesty is part of faith."Ahmad bin Mani said in his version of the hadith that the Prophet ﷺ heard a man admonishing his brother about modesty.He said, "This is a hasan sahih hadith."
حدثنا ابن أبي عمر وأحمد بن منيع المعنى واحد قالا حدثنا سفيان بن عيينة عن الزهري
أن رسول الله ﷺ مر برجل وهو يعظ أخاه في الحياء فقال رسول الله ﷺ الحياء من الإيمان قال أحمد بن منيع في حديثه إن النبي ﷺ سمع رجلا يعظ أخاه في الحياء قال هذا حديث حسن صحيح
Agreed upon (by Bukhari and Muslim). Muslim also narrated it, no. 36, from the hadith of Sufyan bin Uyayna, and Bukhari, no. 24, from the hadith of Zuhri, with the same wording.On this topic there are also narrations from Abu Hurairah [previously mentioned: 2009], Abu Bakra [Ibn Majah, no. 4184], and Abu Umama [previously mentioned: 2027].