Yazid bin al-Asamm said: "I saw the Mother of the Believers Maymunah (may Allah be pleased with her) shaving her head after the Messenger of Allah (peace and blessings be upon him)." I asked Yazid bin al-Asamm (the reason), and he said: "I think she was adopting simplicity."
Hadith Referenceالمعجم الكبير للطبراني / مسند النساء / 20324