Jabir bin'Abdullah (RA) reported Allah's Messenger (ﷺ) as saying: None of you should lie on his back and place one of his feet upon the other.
Related hadith on this topic
Explanation & Benefits
Shaykh Dr. Abdur Rahman Freywai
Explanation:
1:
The prohibition mentioned in this hadith pertains to the situation where there is a fear of exposure (immodesty).
If this is not the case—for example, if a person is wearing pajamas, shalwar, etc.—then there is no harm in lying on one's back with one leg placed over the other,
as has been described regarding the Prophet sallallahu alayhi wa sallam in the previous hadith.
Source: Sunan al-Tirmidhi – Majlis ‘Ilmi Dar al-Da‘wah, New Delhi Edition, Page: 2766
Shaykh Umar Farooq Saeedi
Benefits and Issues:
Because there is a risk of immodesty in this, and performing such an act in the presence of others in a gathering is generally considered inappropriate.
However, its permissibility also exists, especially when there is no fear of immodesty.
As is mentioned in the following narrations.
Source: Sunan Abu Dawood – Commentary by Shaykh Umar Farooq Saeedi, Page: 4865