Jami` at-Tirmidhi, Book 43, Hadith 3028 (In-Book) ⓘ
Narrated Abu Az-Zinad: "Ibn Jarhad informed me from his father, that the Prophet passed by him while his thigh was exposed, so the Prophet said: 'Cover your thigh, for indeed it is 'Awrah.'"
حَدَّثَنَا الْحَسَنُ بْنُ عَلِيٍّ الْخَلاَّلُ، حَدَّثَنَا عَبْدُ الرَّزَّاقِ، أَخْبَرَنَا مَعْمَرٌ، عَنْ أَبِي الزِّنَادِ، أَخْبَرَنِي ابْنُ جَرْهَدٍ، عَنْ أَبِيهِ، أَنَّ النَّبِيَّ صلى الله عليه وسلم مَرَّ بِهِ وَهُوَ كَاشِفٌ عَنْ فَخِذِهِ فَقَالَ النَّبِيُّ صلى الله عليه وسلم " غَطِّ فَخِذَكَ فَإِنَّهَا مِنَ الْعَوْرَةِ " . قَالَ أَبُو عِيسَى هَذَا حَدِيثٌ حَسَنٌ .
also referenced under: Hadith 2798 (Reference) & Volume 5, Book 41, Hadith 2798 (DarusSalam)