The Messenger of Allah ﷺ set out on the expedition to Khaybar. We prayed the dawn prayer near it in the dim light before sunrise, then the Prophet of Allah ﷺ mounted, and Abu Talha mounted, and I rode behind Abu Talha. The Prophet of Allah ﷺ urged his mount through the alleys of Khaybar, and my knee was touching the thigh of the Prophet of Allah ﷺ. Then the lower garment slipped from his thigh until I could see the whiteness of the Prophet of Allah's thigh.When he entered the town he said, "Allah is the greatest! Khaybar is destroyed. When we descend upon the courtyard of a people, evil is the morning of those who were warned."
أن رسول الله ﷺ غزا خيبر، قال: فصلينا عندها صلاة الغداة بغلس، فركب نبي الله ﷺ، وركب أبو طلحة وأنا رديف أبي طلحة، فأجرى نبي الله ﷺ في زقاق خيبر، وإن ركبتي لتمس فخذ نبي الله ﷺ، ثم حسر الإزار عن فخذه حتى إني أنظر إلى بياض فخذ نبي الله ﷺ، فلما دخل القرية قال الله أكبر! خربت خيبر، إنا إذا نزلنا بساحة قوم فساء صباح المنذرين.
Bukhari related it in the Book of Prayer (371) and Muslim in the Book of Marriage (1365:84), both through the route of Ismail bin Ulaya, from Abdul-Aziz bin Suhayb, from Anas, who said, then he mentioned it. The wording given is Bukhari's. In Muslim's wording, and likewise in Ahmad (11992), it reads, "and the waist wrap slipped off the thigh of the Prophet of Allah ﷺ" instead of "then he uncovered the waist wrap from his thigh." His statement "and the waist wrap slipped off" means this happened without his intending or choosing it ﷺ.As for what is mentioned that the thigh is part of the private area, based on the hadith of Ibn Abbas, Jurhud, and Muhammad bin Jahsh, all of these narrations are defective. Bukhari, may Allah have mercy on him, said in the Book of Prayer, in the chapter on what is mentioned regarding the thigh, "It is narrated from Ibn Abbas, Jurhud, and Muhammad bin Jahsh, from the Prophet ﷺ, 'The thigh is part of the private area,' while Anas bin Malik said, 'The Prophet uncovered his thigh.'" Abu Abdullah said, "The hadith of Anas has a stronger chain of transmission, while the hadith of Jurhud is more cautious, until one emerges from their disagreement." End of quote.Bukhari, may Allah have mercy on him, is indicating that the hadiths of these narrators stating that the thigh is part of the private area are not sound, and he is correct, for each of these hadiths contains defects. Zaylai explained the defects of these hadiths in Nasb Raya (4/241–243). After studying these defects, it became clear to me that none of them meet the standard of the Jami Kamil, and so I set aside the task of documenting them, even though their combined weight indicates that there is some basis to the matter, since none of their narrators is accused of fabrication.It is possible to reconcile these hadiths with the hadith of Amr bin Shuayb, from his father, from his grandfather, as a marfu narration, "The private area of a slave is from the navel to the knee," which has been documented elsewhere, by saying that the hadith of Anas indicates that the thigh is not part of the private area, and that the private area consists only of the two private parts, while the hadith of Amr bin Shuayb is to be understood as a matter of caution, meaning the thigh would then be considered part of the private area because it falls within what is between the navel and the knee. This is what Bukhari was pointing to when he said, "The hadith of Anas has a stronger chain" (meaning that the thigh is not part of the private area), "while the hadith of Jurhud is more cautious" (meaning that the thigh is part of the private area).I then came across the words of Hafiz bin Qayyim, "The way to reconcile these hadiths is what several of the companions of Ahmad and others have mentioned, that there are two private areas, a lesser one and a greater one. The greater one consists of the two private parts, while the lesser one consists of the two thighs. There is no contradiction between the command to lower one's gaze from the two thighs, since they are a private area, and their being uncovered, since they are only a lesser private area." Tahzib Sunan (6/17).