The Book of Fasting
13/34. Chapter:
The Prophet's Fasts at times other than Ramadan; and it is recommended to ensure that no month is free of fasting
Sahih Muslim
وَحَدَّثَنَا قُتَيْبَةُ، حَدَّثَنَا حَمَّادٌ، عَنْ أَيُّوبَ، عَنْ عَبْدِ اللَّهِ بْنِ شَقِيقٍ، قَالَ سَأَلْتُ عَائِشَةَ - رضى الله عنها - بِمِثْلِهِ وَلَمْ يَذْكُرْ فِي الإِسْنَادِ هِشَامًا وَلاَ مُحَمَّدًا .
A hadith like this has been narrated on the authority of Abdullah b. Shaqiq but in the chain of transmitters no mention is made of Hisham and Muhammad.
Reference : Sahih Muslim 1156dIn-book reference : Book 13, Hadith 226USC-MSA web (English) reference : Book 6, Hadith 2579