Is It Haram to Sleep Naked?

The ‘awrah must be covered in all circumstances except when necessary, such as when bathing, having intercourse, relieving oneself, etc. But when there is no reason, the ‘awrah must be covered, because of the report narrated by Bahz ibn Hakeem from his father, from his grandfather, who said: “O Messenger of Allah, what should we do about our ‘awrahs?” He said, “Guard you ‘awrah except from your wives and those whom your right hand possesses (concubines).” He asked, “What about when a man is with another man?” He said, “If you can manage not to let anyone see it, then do that.” He asked, “What if one of us is alone?’ He said, “Allah is more deserving that you should feel shy before Him.” (Narrated by al-Tirmidhi, 2769, and others). 

Based on the above, it is not permissible for you to sleep with no clothes on that would cover your ‘awrah, whether you are sleeping with or without your wife. Rather it is permissible for you to uncover your ‘awrah only at times of necessity.

And Allah knows best.