Jarhad reported that the Prophet ﷺ passed by him in the mosque while his thigh was uncovered, and he said, "The thigh is part of the private area."
حدثنا ابن أبي عمر حدثنا سفيان عن أبي النضر مولى عمر بن عبيد الله
جرهد قال مر النبي ﷺ بجرهد في المسجد وقد انكشف فخذه فقال إن الفخذ عورة
[Hasan]. Humaydi narrated it, no. 859, from Sufyan bin Uyayna, and Abu Dawud, no. 4014, narrated it from the hadith of Abu Nadr, through the same chain. Bukhari mentioned it without a full chain in his chapter on prayer, chapter 12. Ibn Hibban graded it sahih, no. 353, as did Hakim, 4/180, and Dhahabi agreed with him, but Bukhari and others graded it daif. The hadith has supporting reports, including the one that follows (2792).