مِشْكَاةُ الْمَصَابِيحِ
Mishkat al-Masabih 468
Purification
Associating with one who is defiled, and what is permitted - Section 3
عَنْ أُمِّ سَلَمَةَ رَضِيَ اللَّهُ عَنْهَا قَالَتْ: كَانَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ يُجْنِبُ ثُمَّ يَنَامُ ثُمَّ يَنْتَبِهُ ثُمَّ يَنَامُ. رَوَاهُ أَحْمد
Umm Salama said that God’s messenger would become defiled, then go to sleep, then awake, then go to sleep again. Ahmad transmitted it.
Mishkat al-Masabih, 468ضَعِيف (الألباني)