It was narrated from Ibn `Umar that `Umar bin al-Khattab (رضي الله عنه) said:
I asked the Messenger of Allah (ﷺ) : O Messenger of Allah (ﷺ), if one of us wants to sleep before doing ghusl when he is junub, what should he do? He said: `Let him do wudoo’ as for prayer, then sleep.”