It is narrated from Sayyida Aisha (may Allah be pleased with her), she says: My practice was that I used to make up the missed fasts of Ramadan in Sha'ban, until the Messenger of Allah (peace and blessings be upon him) passed away.
Hadith Referenceالفتح الربانی / كتاب الصيام / 3853
Hadith Gradingمحدثین:صحیح
Hadith Takhrij«اخرجه البخاري: 1950، ومسلم: 1146، (انظر مسند أحمد ترقيم الرسالة: 24999 ترقیم بيت الأفكار الدولية: 25513»
Brief Explanation
Benefits: … Regarding the making up (qada) of missed fasts in Ramadan, Allah the Exalted has said: {فَـعِـدَّۃٌمِّـنْاَیَّامٍاُخَرَ} “The number (should be made up) on other days.” (Surah al-Baqarah: 184) This verse is absolute; no restriction of any kind has been placed in it. Whereas Sayyidah Aisha radi Allahu anha used to make up her missed fasts in Sha’ban after ten months, therefore, the missed fasts can be made up at any time, and it is permissible to delay them until after the next Ramadan. However, the scholars are unanimous that delaying them until after the next Ramadan without a valid excuse is disliked (makruh). It is a separate matter that in many verses and hadiths, encouragement has been given to fulfill such obligations quickly, because there is no knowledge of death or illness.