Bukhari

Hadith Commentary:
In a narration from Jabir radi Allahu anhu, it is reported that the Messenger of Allah sallallahu alayhi wa sallam forbade a person from lying on his back with one leg placed over the other.
(Sahih Muslim, Kitab al-Libas wa al-Zinah, Hadith: 5499(2099))

This hadith appears to be in contradiction to the aforementioned hadith, but reconciliation between these two ahadith is as follows: when a person lies on his back and his private parts become exposed, then it is prohibited, as is mentioned in the hadith of Sahih Muslim. However, if the private parts are not exposed, then it is permissible, as is indicated in the aforementioned hadith of Sahih al-Bukhari. Therefore, there is no contradiction between these ahadith.

And Allah knows best.

Hadith Commentary:

Benefits and Issues:
We have already explained its form in the previous chapter, that is, placing one foot over the other is permissible; however, raising the knee and placing the foot upon it is not correct.

722. Commentary: In one narration, there is also a prohibition against lying on one’s back with one leg placed over the other. See: [صحیح مسلم ، اللباس ، حدیث : (72) – 2099]
According to some scholars, reconciliation between the two narrations is as follows: if the legs are extended, then lying down with one leg over the other is permissible, because in this way proper covering (of the awrah) is maintained. However, if the knees are raised and one leg is placed over the other, then this is prohibited, because this posture appears indecent. According to Imam Khattabi rahimahullah, the hadith containing the prohibition is abrogated, but there should be evidence for this claim. The preferred opinion is that if proper covering is maintained, then it is permissible to lie on one’s back in any manner with one leg over the other; there is no harm in this, it is allowed, and it is established from the Prophet sallallahu alayhi wa sallam.