Hadithcore
Mishkat al-Masabih, 468

Umm Salama said that God’s messenger would become defiled, then go to sleep, then awake, then go to sleep again. Ahmad transmitted it.

عَنْ أُمِّ سَلَمَةَ رَضِيَ اللَّهُ عَنْهَا قَالَتْ: كَانَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ يُجْنِبُ ثُمَّ يَنَامُ ثُمَّ يَنْتَبِهُ ثُمَّ يَنَامُ. رَوَاهُ أَحْمد

References1 variant
In-Book Reference
Book 3, Hadith 172