وَحَدَّثَنِي عَنْ مَالِكٍ، عَنْ هِشَامِ بْنِ عُرْوَةَ، عَنْ أَبِيهِ، عَنْ عَائِشَةَ، زَوْجِ النَّبِيِّ صلى الله عليه وسلم أَنَّهَا كَانَتْ تَقُولُ إِذَا أَصَابَ أَحَدُكُمُ الْمَرْأَةَ ثُمَّ أَرَادَ أَنْ يَنَامَ قَبْلَ أَنْ يَغْتَسِلَ فَلاَ يَنَمْ حَتَّى يَتَوَضَّأَ وُضُوءَهُ لِلصَّلاَةِ ‏.‏

Yahya related to me from Malik from Hisham ibn Urwa from hisfather that A'isha, the wife of the Prophet, may Allah bless him andgrant him peace, used to say, "If you have intercourse with your wifeand then wish to go to sleep before doing ghusl, do not sleep untilyou have done wudu as for prayer." Translation Not Available

Book Ref: Muwatta Imam Malik Book 2 Hadith 109
Web Ref:  Muwatta Imam Malik Book 2 Hadith 79