It is narrated from the grandson of Sayyiduna Jarhad (may Allah be pleased with him), from his father, from his grandfather, that the Prophet (peace and blessings be upon him) sat with him - and he was one of the People of the Suffah - and the Prophet (peace and blessings be upon him) saw his thigh uncovered and said: "Cover your thigh, for the thigh is awrah."
Hadith Referenceالمعجم الكبير للطبراني / باب الجيم / 2131