Sahih Muslim Book 3, Hadith Number 648.

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 he should wash herself after the menstrual period. He (the Holy Prophet) said: Take a cotton with musk and purity yourself, and the rest of the Hadith was narrated like that of Sufyan.