"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.'" (Using translation from Tirmidhī 2798)
أَنَّ النَّبِيَّ ﷺ مَرَّ بِهِ وَهُوَ كَاشِفٌ عَنْ فَخِذِهِ فَقَالَ «غَطِّهَا فَإِنَّهَا مِنَ الْعَوْرَةِ»