Hadith 3:157
‘Aisha said that when the Prophet was defiled and wanted to eat or sleep, he performed the ablution prescribed for prayer. (Bukhari and Muslim)
وَعَنْ عَائِشَةَ رَضِيَ اللَّهُ عَنْهَا قَالَتْ: كَانَ النَّبِيُّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ إِذَا كَانَ جُنُبًا فَأَرَادَ أَنْ يَأْكُلَ أَوْ ينَام تَوَضَّأ وضوءه للصَّلَاة
Original Reference: Mishkat al-Masabih 453