كتاب الصيام
13
The Book of Fasting
(26)
Chapter: It is Permissible to delay making up missed Ramadan Fasts until before the next Ramadan comes, and this is for those who broke the fast for a reason such as sickness, travel, menstruation and the like
(26)
باب قَضَاءِ رَمَضَانَ فِي شَعْبَانَ ‏

'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.
وَحَدَّثَنِي مُحَمَّدُ بْنُ أَبِي عُمَرَ الْمَكِّيُّ، حَدَّثَنَا عَبْدُ الْعَزِيزِ بْنُ مُحَمَّدٍ الدَّرَاوَرْدِيُّ، عَنْ يَزِيدَ بْنِ عَبْدِ اللَّهِ بْنِ الْهَادِ، عَنْ مُحَمَّدِ بْنِ إِبْرَاهِيمَ، عَنْ أَبِي سَلَمَةَ بْنِ عَبْدِ الرَّحْمَنِ، عَنْ عَائِشَةَ، - رضى الله عنها - أَنَّهَا قَالَتْ إِنْ كَانَتْ إِحْدَانَا لَتُفْطِرُ فِي زَمَانِ رَسُولِ اللَّهِ صلى الله عليه وسلم فَمَا تَقْدِرُ عَلَى أَنْ تَقْضِيَهُ مَعَ رَسُولِ اللَّهِ صلى الله عليه وسلم حَتَّى يَأْتِيَ شَعْبَانُ ‏.‏
Reference : Sahih Muslim 1146 e
In-book reference : Book 13, Hadith 197
USC-MSA web (English) reference : Book 6, Hadith 2552
  (deprecated numbering scheme)