أَخْبَرَنَا الْحَسَنُ بْنُ مُحَمَّدٍ، قَالَ حَدَّثَنَا عَفَّانُ، قَالَ حَدَّثَنَا وُهَيْبٌ، قَالَ حَدَّثَنَا مَنْصُورُ بْنُ عَبْدِ الرَّحْمَنِ، عَنْ أُمِّهِ، صَفِيَّةَ بِنْتِ شَيْبَةَ عَنْ عَائِشَةَ، أَنَّ امْرَأَةً، سَأَلَتِ النَّبِيَّ صلى الله عليه وسلم قَالَتْ يَا رَسُولَ اللَّهِ كَيْفَ أَغْتَسِلُ عِنْدَ الطُّهُورِ قَالَ ‏"‏ خُذِي فِرْصَةً مُمَسَّكَةً فَتَوَضَّئِي بِهَا ‏"‏ ‏.‏ قَالَتْ كَيْفَ أَتَوَضَّأُ بِهَا قَالَ ‏"‏ تَوَضَّئِي بِهَا ‏"‏ ‏.‏ قَالَتْ كَيْفَ أَتَوَضَّأُ بِهَا قَالَتْ ثُمَّ إِنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم سَبَّحَ وَأَعْرَضَ عَنْهَا فَفَطِنَتْ عَائِشَةُ لِمَا يُرِيدُ رَسُولُ اللَّهِ صلى الله عليه وسلم قَالَتْ فَأَخَذْتُهَا وَجَبَذْتُهَا إِلَىَّ فَأَخْبَرْتُهَا بِمَا يُرِيدُ رَسُولُ اللَّهِ صلى الله عليه وسلم ‏.‏

It was narrated from 'Aishah: "A woman asked the Prophet (PBUH): 'O Messenger of Allah, how should I perform Ghusl when I become pure?' He said: 'Take a piece of cotton wool scented with musk and clean yourself with it.' She said: 'How should I clean myself with it?' He said: 'Clean yourself with it.' She said: "How should I clean myself with it?' The Messenger of Allah (PBUH) said: 'Subhan Allah!' and turned away from her." 'Aishah understood what the Messenger of Allah (PBUH) meant, and said: "So I pulled her toward me and told her what the Messenger of Allah (PBUH) meant." Translation Not Available

Book Ref: Sunan An Nisai Book 4 Hadith 427
Web Ref:  Sunan An Nisai Vol 1 Book 4 Hadith 427