كتاب الحيض
3  
The Book of Menstruation
(10)
Chapter: The amount of water with which it is recommended to perform ghusl in the case of janabah; a man and woman washing from a single vessel; one of them washing with the left-over water of the other
(10)
باب الْقَدْرِ الْمُسْتَحَبِّ مِنَ الْمَاءِ فِي غُسْلِ الْجَنَابَةِ وَغُسْلِ الرَّجُلِ وَالْمَرْأَةِ فِي إِنَاءٍ وَاحِدٍ فِي حَالَةٍ وَاحِدَةٍ وَغُسْلِ أَحَدِهِمَا بِفَضْلِ الآخَرِ
Sahih Muslim 321 a

Salama b. Abd al-Rahman narrated it on the authority of A'isha that when the Messenger of Allah (ﷺ) took a bath, he started from the right hand and poured water over it and washed it, and then poured water on the impurity with the right band and washed it away with the help of the left hand. and after having removed it, he poured water on his head. A'isha said:

I and the Messenger of Allah (ﷺ) took a bath from the same vessel, after sexual intercourse.
حَدَّثَنَا هَارُونُ بْنُ سَعِيدٍ الأَيْلِيُّ، حَدَّثَنَا ابْنُ وَهْبٍ، أَخْبَرَنِي مَخْرَمَةُ بْنُ بُكَيْرٍ، عَنْ أَبِيهِ، عَنْ أَبِي سَلَمَةَ بْنِ عَبْدِ الرَّحْمَنِ، قَالَ قَالَتْ عَائِشَةُ كَانَ رَسُولُ اللَّهِ صلى الله عليه وسلم إِذَا اغْتَسَلَ بَدَأَ بِيَمِينِهِ فَصَبَّ عَلَيْهَا مِنَ الْمَاءِ فَغَسَلَهَا ثُمَّ صَبَّ الْمَاءَ عَلَى الأَذَى الَّذِي بِهِ بِيَمِينِهِ وَغَسَلَ عَنْهُ بِشِمَالِهِ حَتَّى إِذَا فَرَغَ مِنْ ذَلِكَ صَبَّ عَلَى رَأْسِهِ ‏.‏ قَالَتْ عَائِشَةُ كُنْتُ أَغْتَسِلُ أَنَا وَرَسُولُ اللَّهِ صلى الله عليه وسلم مِنْ إِنَاءٍ وَاحِدٍ وَنَحْنُ جُنُبَانِ ‏.‏
Reference : Sahih Muslim 321a
In-book reference : Book 3, Hadith 51
USC-MSA web (English) reference : Book 3, Hadith 627
  (deprecated numbering scheme)