Can I sleep in a state of janabah?

What janabah means

Janabah is the state of major ritual impurity after sexual intercourse or any release of semen, including a wet dream. In this state you can't pray, touch the Quran (for most scholars) or stay in the prayer hall of a mosque until you take a ghusl, the full-body wash. But it doesn't make you "dirty" as a person, and it doesn't stop normal life like eating, sleeping or talking. See When is ghusl required?

The Prophet's ﷺ practice

Umar ibn al-Khattab asked the Prophet ﷺ whether one of them could sleep while in janabah. He replied, "Yes, if he performs wudu, he can sleep while in janabah" (Sahih al-Bukhari 287). Aishah also described that when he wanted to sleep in that state, he would wash his private parts and make wudu like the wudu for prayer (Sahih al-Bukhari 288).

The four schools agree this wudu is recommended (sunnah), not obligatory. Some early scholars, and a view among the Zahiris, held it to be required, but the majority understood the wording as encouragement. So if you're exhausted and fall asleep, you haven't sinned.

Why wudu before sleeping helps

• It lightens the state of impurity, as scholars describe it.
• It follows the general sunnah of sleeping in wudu, along with the bedtime adhkar. See What should I say before sleeping?
• It refreshes you and makes it easier to get up for ghusl and Fajr.

The same applies if you want to eat or sleep again after intimacy: a quick wash and wudu is the sunnah way.

Don't let it make you miss Fajr

The real rule is about prayer, not sleep. Ghusl must be done before the next prayer time ends. If you wake up near sunrise, take a quick ghusl and pray straight away. A ghusl doesn't need to be long: rinse your mouth and nose, and let water reach your whole body. See How do I do ghusl? If you wake from a wet dream at night, you can go back to sleep too and take ghusl in the morning. See Do I need ghusl after a wet dream?