The Prophet ﷺ said, "Whoever fasts perpetually has not truly fasted."
حدثنا أبو نعيم حدثنا سفيان عن حبيب عن أبي العباس
عن النبي ﷺ قال لا صام من صام الأبد
No references are available.
Its isnad is sahih. Sufyan is Thawri, and Habib is Ibn Abu Thabit. The hadith is abridged from 6789 and 6874, and it is one of the narrations of the longer hadith 6477. We failed to point this out there.