Regarding man’s `awrah in front of others, with the exception of his wife, there are many ahadith which indicate that a man’s ‘awrah is the area between the navel and the knee while the navel and knee are not part of the ‘awrah.
These ahadith include the following:
1 – Abu Dawood and Ibn Majah narrated that ‘Ali (may Allah be pleased with him) said: The Messenger of Allah (peace and blessings be upon him) said: “Do not show your thigh, and do not look at the thigh of anyone, living or dead.” (Sunan Abu Daud and Musnad Ahmad)
2 – Ahmad narrated that Muhammad ibn Jahsh (may Allah be pleased with him) said: The Prophet (peace and blessings be upon him) passed by Ma’mar when I was with him, and his thighs were uncovered. He said: “O Ma’mar, cover your thighs, for the thigh is ‘awrah.” (Musnad Ahmad)
3 – Ahmad, Abu Dawood and al-Tirmidhi narrated from Jawhad al-Aslami that the Prophet (peace and blessings be upon him) passed by him when his thigh was uncovered and he said: “Do you not know that the thigh is ‘awrah?” (Sunan al-Kubra)
4 – al-Tirmidhi narrated from Ibn ‘Abbas (may Allah be pleased with him) that the Prophet (peace and blessings be upon him) said: “The thigh is ‘awrah.” (Sunan al-Sughra)