The Prophet ﷺ used to fast until people would say he never broke his fast, and he would refrain from fasting until people would say he never fasted.
حدثنا روح حدثنا حماد عن ثابت
أن النبي ﷺ كان يصوم حتى يقال قد صام ويفطر حتى يقال قد أفطر
Its isnad is sahih, mentioned previously at 12768.