Sahih Muslim Book 003, Hadith Number 0647.
Chapter : The desirability of using musk at the spot of blood while bathing after menstruation.
'Aisha reported: A woman asked the Apostle of Allah (may peace be upon him) how to wash herself after menstruation. She mentioned that he taught her how to take bath and then told her to take a piece of cotton with musk and purify herself. She said: How should I purify myself with that? He (the Holy Prophet) said: Praise be to Allah, purify yourself with it, and covered his face, Sufyan b. 'Uyaina gave a demonstration by covering his face (as the Holy Prophet had done). 'Aisha reported: I dragged her to my side for I had understood what the Apostle of Allah (may peace be upon him) intended and, therefore, said: Apply this cotton with musk to the trace of blood. Ibn 'Umar in his Hadith (has mentioned the words of 'Aisha thus): Apply it to the marks of blood.