(21) باب الاِحْتِبَاءِ فِي ثَوْبٍ وَاحِدٍ
Narrated Abu Sa`id Al-Khudri:
The Prophet (ﷺ) forbade Ishtimal-as-Samma' and that a man should sit in an Ihtiba' posture in one garment, nothing of which covers his private parts.
Reference: Sahih al-Bukhari 5822
In-book reference: Book 77, Hadith 39
USC-MSA web (English) reference(deprecated numbering scheme): Vol. 7, Book 72, Hadith 712