Hadith 506450
Chapter 18: Fasting - كتاب الصيام
وَحَدَّثَنِي عَنْ مَالِكٍ، عَنْ سُمَىٍّ، مَوْلَى أَبِي بَكْرٍ عَنْ أَبِي بَكْرِ بْنِ عَبْدِ الرَّحْمَنِ، عَنْ عَائِشَةَ، وَأُمِّ سَلَمَةَ زَوْجَىِ النَّبِيِّ صلى الله عليه وسلم أَنَّهُمَا قَالَتَا إِنْ كَانَ رَسُولُ اللَّهِ صلى الله عليه وسلم لَيُصْبِحُ جُنُبًا مِنْ جِمَاعٍ غَيْرِ احْتِلاَمٍ ثُمَّ يَصُومُ .
Yahya related to me from Malik from Sumayy, the mawla of Abu Bakr, from Abu Bakr ibn Abd ar-Rahman that A'isha and Umm Salama, the wives of the Prophet, may Allah bless him and grant him peace, said, "The Messengerof Allah, may Allah bless him and grant him peace, used to get up in the morning junub from intercourse, not a dream, and would then fast."
Reference Muwatta Malik 506450
USC-MSA web (English) reference : Book 18, Hadith 12