Whenever the Prophet (ﷺ) intended to sleep while he was Junub, he used to wash his private parts and perform ablution like that for the prayer.
Sahih al-Bukhari Book 5, Hadith 40
← Previous Hadith I asked Allah's Messenger (ﷺ) "Can any one of us sleep while he is Junub?" He replied, "Yes, if he performs ablution, he can sleep while he is Junub."

Sahih al-Bukhari Book 5, Hadith 39 Next Hadith → `Umar asked the Prophet (ﷺ) "Can anyone of us sleep while he is Junub?" He replied, "Yes, if he performs ablution."

Sahih al-Bukhari Book 5, Hadith 41