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 ‏
Sahih Muslim 1146 b

This hadith is narrated on the authority of Yahya b. Sa'id with the same chain of transmitters but with this variation that he said that ('A'isha did not observe fast but in Sha'ban) out of regard for the Messenger of Allah (ﷺ).

وَحَدَّثَنَا إِسْحَاقُ بْنُ إِبْرَاهِيمَ، أَخْبَرَنَا بِشْرُ بْنُ عُمَرَ الزَّهْرَانِيُّ، حَدَّثَنِي سُلَيْمَانُ، بْنُ بِلاَلٍ حَدَّثَنَا يَحْيَى بْنُ سَعِيدٍ، بِهَذَا الإِسْنَادِ غَيْرَ أَنَّهُ قَالَ وَذَلِكَ لِمَكَانِ رَسُولِ اللَّهِ صلى الله عليه وسلم ‏.‏
Reference : Sahih Muslim 1146b
In-book reference : Book 13, Hadith 194
USC-MSA web (English) reference : Book 6, Hadith 2550
  (deprecated numbering scheme)