مُسْنَدُ أَحْمَدَ
Musnad Ahmad 2481
Musnad of 'Abdullah bin al-'Abbas bin 'Abdul-Muttalib from the Prophet
It was narrated that Ibn 'Abbas (رضي الله عنه) said: The Messenger of Allah (ﷺ) passed by a man whose thigh was showing. He said: "Cover your thigh, for a man's thigh is part of his ‘awrah."
Musnad Ahmad 2493Hasan lishawahidihi and this is a da'eef isnad]