Answered by Shaykh Faraz Rabbani
Question: Is it permissible for a husband and wife to wear night clothes that don’t usually cover their nakedness (awra) while sleeping?
Answer: In the name of Allah, Most Merciful.
Walaikum assalam wa rahmatullahi wa barakatuh,
It would not be blameworthy to be in such a state when going to sleep under a blanket. Otherwise, both men and women are expected to cover from navel to knee even when alone.
Wassalam,
Faraz Rabbani