Amr bin Dinar (may Allah have mercy on him) said: I heard Jabir bin Abdullah al-Ansari (may Allah be pleased with them both) relate that the Messenger of Allah (peace and blessings be upon him), during the building of the Ka'bah in the pre-Islamic era, was carrying stones with the people. He was wearing a waist-wrapper. His uncle Abbas (may Allah be pleased with him) said: O my nephew! If you were to take off your waist-wrapper and place it on your shoulders beneath the stones (it would be easier for you). Jabir (may Allah be pleased with him) said: He took off the waist-wrapper and put it on his shoulder, and at that very moment he fell down unconscious. After that he was never seen naked.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 3225
Ibn Jurayj transmitted this narration from Amr, and he said that he (peace and blessings be upon him) fell to the ground and his eyes were raised towards the sky. Then he (peace and blessings be upon him) stood up and said: "My waist-wrapper, my waist-wrapper!" Then he (peace and blessings be upon him) tied on his waist-wrapper.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 3226
It is narrated from Sayyidah Aishah (may Allah be pleased with her) that the Messenger of Allah (peace and blessings be upon him) forbade entering the bathhouses, then permitted men to enter them wearing waist-wrappers.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 3227
Zur'ah bin Abd al-Rahman bin Jarhad narrates from his father that Jarhad (may Allah be pleased with him), who was one of the People of the Suffah, said: The Messenger of Allah (peace and blessings be upon him) was sitting with us and my thigh was uncovered, so he (peace and blessings be upon him) said: "Cover it. Do you not know that the thigh is awrah?"
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 3228
Abd al-Rahman bin Jarhad (may Allah have mercy on him) narrates from his father (Sayyiduna Jarhad, may Allah be pleased with him) that the Prophet (peace and blessings be upon him) passed by him while he had his thigh uncovered. He (peace and blessings be upon him) said: "Keep it covered, for it is awrah."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 3229
Abu Kathir narrates from his master, Muhammad bin Abdullah bin Jahsh (may Allah be pleased with him), that he said: I was with the Messenger of Allah (peace and blessings be upon him). He (peace and blessings be upon him) passed by Ma'mar (may Allah be pleased with him), who was sitting near his house in the market with both his thighs uncovered. The Prophet (peace and blessings be upon him) said: "O Ma'mar! Cover your thighs, for the thighs are part of the awrah."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 3230
It is narrated from Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) that the Messenger of Allah (peace and blessings be upon him) said: "The thigh is awrah."
These are sahih (authentic) chains that can be used as proof.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 3231
(a) It is narrated from Sayyiduna Ali (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "Do not uncover your thigh, and do not look at the thigh of anyone, living or dead."
(b) In the narration of Rawh: The Messenger of Allah (peace and blessings be upon him) came to me while my thigh was uncovered, and he (peace and blessings be upon him) said: "O Ali! Cover your thigh, for it is awrah."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 3232
Amr bin Shu'ayb narrates from his father, and he from his grandfather (may Allah be pleased with him), that the Messenger of Allah (peace and blessings be upon him) said: "When children reach seven years of age, command them to pray; and when they reach ten years of age and do not pray, punish them; and separate their beds. And when one of you marries off a slave or a hired worker, then let her never look at the area from his navel to his knees, for from the navel to the knees is awrah."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 3233
Amr bin Shu'ayb narrates from his father, and he from his grandfather (may Allah be pleased with him), that the Messenger of Allah (peace and blessings be upon him) said: "Command your children to pray at the age of seven, punish them for not praying at the age of ten, and separate their beds. And when one of you marries off his slave, his slave-girl or his hired worker, then let the slave-girl never look at any of his awrah, for from the navel to the knees is awrah."
It has also been narrated from Sawwar, from Muhammad bin Juhadah, from Amr, but that is of no worth.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 3234
Amr bin Shu'ayb narrates from his father, and he from his grandfather (may Allah be pleased with him), that the Messenger of Allah (peace and blessings be upon him) said: "When your children reach seven years of age, teach them to pray; punish them for not praying at the age of ten; and separate their sleeping places. And when one of you marries his slave-girl to his servant or hired worker, then let her not look at his awrah, and the awrah is between the navel and the knees."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 3235
Amr bin Shu'ayb narrates from his father, and he from his grandfather, that the Messenger of Allah (peace and blessings be upon him) said: "Teach children to pray at the age of seven, punish them for not praying at the age of ten, and separate their beds. And when you marry your slave-girl to your slave or servant, then never look at his awrah; and the awrah is the area between the navel and the knee."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 3236
Sayyiduna Abu Ayyub (may Allah be pleased with him) relates: I heard the Messenger of Allah (peace and blessings be upon him) say: "Whatever is above the knees is awrah, and whatever is below the navel is awrah."
Sa'id bin Abi Rashid al-Basri, who narrated it, is da'if (weak).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 3237