Muwatta Imam Malik Book of Fasting, Hadith 10

Yahya related to me from Malik from Abd Rabbih ibn Said from Abu Bakr ibn Abd ar-Rahman ibn al-Harith ibn Hisham from A'isha and Umm Salama, the wives of the Prophet ﷺ that the Prophet ﷺ used to get up in the morning junub from intercourse, not a dream, in Ramadan, and then he would fast."

وَحَدَّثَنِي عَنْ مَالِكٍ، عَنْ عَبْدِ رَبِّهِ بْنِ سَعِيدٍ، عَنْ أَبِي بَكْرِ بْنِ عَبْدِ الرَّحْمَنِ بْنِ الْحَارِثِ بْنِ هِشَامٍ، عَنْ عَائِشَةَ، وَأُمِّ سَلَمَةَ زَوْجَىِ النَّبِيِّ ﷺ أَنَّهُمَا قَالَتَا كَانَ رَسُولُ اللَّهِ ﷺ يُصْبِحُ جُنُبًا مِنْ جِمَاعٍ غَيْرِ احْتِلاَمٍ فِي رَمَضَانَ ثُمَّ يَصُومُ .