"Ibn Jarhad informed me from his father, that the Prophet ﷺ passed by him while his thigh was exposed, so the Prophet ﷺ said: 'Cover your thigh, for indeed it is 'Awrah.'"  

أَنَّ النَّبِيَّ ﷺ مَرَّ بِهِ وَهُوَ كَاشِفٌ عَنْ فَخِذِهِ فَقَالَ النَّبِيُّ ﷺ غَطِّ فَخِذَكَ فَإِنَّهَا مِنَ الْعَوْرَةِ  

[Machine] We went out with the Messenger of Allah ﷺ , and a man from the Banu 'Adiy came by us with his thigh exposed. The Messenger of Allah ﷺ said, "Cover your thigh, O Ma'mar, for it is from the 'awrah (that which should be covered)."  

خَرَجْنَا مَعَ رَسُولِ اللهِ ﷺ فَمَرَّ بِنَا رَجُلٌ مِنْ بَنِي عَدِيٍّ كَاشِفٌ عَنْ فَخِذِهِ فَقَالَ رَسُولُ اللهِ ﷺ «غَطِّ فَخِذَكَ يَا مَعْمَرُ فَإِنَّهَا مِنَ الْعَوْرَةِ»