From Sahih Muslim (Hadith 2691):
A'isha reported:If one amongst us had to break fasts (of Ramadan due to natural reasons, i. e. menses) during the life of the Messenger of Allah (ﷺ) she could not find it possible to complete them so long she had been in the presence of Allah's Messenger (ﷺ) till Sha'ban commenced
Reference: Muslim 2691