It is narrated from Sayyiduna Jarid that once he was sitting with his thigh uncovered. The Prophet (ﷺ) passed by and the Prophet (ﷺ) said: Do you not know that the thigh is 'awrah (part of the body that must be covered)?
Hadith Referenceمسند احمد / مسند المكيين / 15926
Hadith Gradingحکم دارالسلام:حسن لشواهده، وهذا إسناد ضعيف، وهو مضطرب جداً