Whenever the Messenger of Allah ﷺ intended to sleep after having sexual intercourse, he performed ablution as for the prayer before going to sleep.
أَنَّ رَسُولَ اللَّهِ ﷺ كَانَ إِذَا أَرَادَ أَنْ يَنَامَ وَهُوَ جُنُبٌ تَوَضَّأَ وُضُوءَهُ لِلصَّلاَةِ قَبْلَ أَنْ يَنَامَ