(21) باب اسْتِخْلاَفِ الإِمَامِ إِذَا عَرَضَ لَهُ عُذْرٌ مِنْ مَرَضٍ وَسَفَرٍ وَغَيْرِهِمَا مَنْ يُصَلِّي بِالنَّاسِ وَأَنَّ مَنْ صَلَّى خَلْفَ إِمَامٍ جَالِسٍ لِعَجْزِهِ عَنِ الْقِيَامِ لَزِمَهُ الْقِيَامُ إِذَا قَدَرَ عَلَيْهِ وَنَسْخِ الْقُعُودِ خَلْفَ الْقَاعِدِ فِي حَقِّ مَنْ قَدَرَ عَلَى الْقِيَامِ
'A'isha, the wife of the Messenger of Allah (ﷺ), said:
I tried to dissuade the Messenger of Allah (ﷺ) from it (i. e. from appointing Abu Bakr as the Imam.) and my insistence upon it was not due to the fact that I entertained any apprehension in my mind that the people would not love the man who would occupy his (Prophet's) place (i. e. who would be appointed as his caliph) and I feared that the people would be superstitious about one who would occupy his place. I, therefore, desired that the Messenger of Allah (ﷺ) should leave Abu Bakr aside in this matter.
Reference: Sahih Muslim 418 d
In-book reference: Book 4, Hadith 101
USC-MSA web (English) reference(deprecated numbering scheme): Book 4, Hadith 835