Evidence that Men’s `Awrah in Islam is from the Navel to the Knee
Question

I need to have some evidence from the sunnah of our beloved prophet that men’s `Awrah is from the navel to the knee. My friend is asking for proof.
Praise be to Allah.What is a Man’s `Awrah?
There are many Hadiths which indicate that a man’s `Awrah is the area between the navel and the knee (and the navel and knee are not part of the `Awrah). (See Al-Majmu`, 3/173; 2/286)
Key Hadiths Supporting Men’s `Awrah being from Navel to Knee
These Hadiths include the following:

Abu Dawud (3140) and Ibn Majah (1460) narrated that `Ali (may Allah be pleased with him) said: The Messenger of Allah (peace and blessings of Allah be upon him) said: “Do not show your thigh, and do not look at the thigh of anyone, living or dead.”
Ahmad (21989) narrated that Muhammad ibn Jahsh (may Allah be pleased with him) said: The Prophet (peace and blessings of Allah 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.”
Ahmad (15502), Abu Dawud (4014) and At-Tirmidhi (2798) narrated from Jawhad Al-Aslami (may Allah be pleased with him) that the Prophet (peace and blessings of Allah be upon him) passed by him when his thigh was uncovered and he said: “Do you not know that the thigh is `Awrah?”
At-Tirmidhi (2798) narrated from Ibn `Abbas (may Allah be pleased with him) that the Prophet (peace and blessings of Allah be upon him) said: “The thigh is (part of) `Awrah ”

Scholarly Analysis of Men’s `Awrah in Islam
Shaykh Al-Albani (may Allah have mercy on him) said concerning these Hadiths in Al-Irwa’ (1/297):
Although their chains of narration are not entirely free of weakness, they strengthen one another, because there is no narrator among them who may be regarded as suspicious, rather their weakness has to do with confusion and ambiguity. And there are similar reports which make one confident that the Hadith is authentic, especially since some of them were classed as authentic by Al-Hakim, and Adh-Dhahabi agreed with him. And Al-Bukhari narrated it in a Mu`allaq report in his Sahih… But a number of these chains of narration give the Hadith strength, and raise it to the level of being authentic, especially since there are similar, corroborating reports on the same issue. (End quote)
It says in Fatawa Al-Lajnah Ad-Da’imah (6/165):
Even though there is some weakness in the chains of narration of these Hadiths, as there are gaps in the chain of narrators or there is some weakness in some of the narrators, nevertheless they support one another, and when taken as a whole they provide the required evidence. (End quote)
The majority of jurists are of the view that these Hadiths should be followed and they stated that a man’s `Awrah is from the navel to the knee. (See Al-Mughni, 2/284)
See the answers below for further clarification:
Men’s ‘awrah and wearing pants with shirt tucked in
`Awrah for Men: Why Is the Man’s Chest Not Included?
What is the ruling on trousers that show the shape of a man’s `Awrah?
And Allah knows best.