Hadith: Modesty brings nothing but good

عن عمران بن حصين رضي الله عنهما قَالَ: قَالَ رسولُ اللَّه -صَلّى اللهُ عَلَيْهِ وسَلَّم-: «الحَيَاءُ لاَ يَأْتِي إِلاَّ بِخَيرٍ». وفي رواية : «الحَيَاءُ خَيرٌ كُلُّهٌ» أو قال: «الحَيَاءُ كُلُّهُ خَيرٌ».
[صحيح] - [الرواية الأولى: متفق عليها. الرواية الثانية والثالثة: رواها مسلم]

‘Imrān ibn Husayn (may Allah be pleased with him) reported that the Messenger (may Allah's peace and blessings be upon him) said: "Modesty brings nothing but good." In another narration: "All of modesty is good."
Sahih/Authentic. - [Muslim]

Explanation

Modesty is the kind of trait that induces humans to perform actions that beautify and adorn and to abandon actions that defile and dishonor. Hence, it brings nothing but good. The reason the Prophet (may Allah's peace and blessings be upon him) said this is because he met someone who was advising his brother against excessive modesty.