The Prophet ﷺ was brought a drink, and it was passed around to the people present. Among them was a man who was fasting. When it reached him, the Prophet ﷺ said to him, "Drink."Someone said, "Messenger of Allah, he does not break his fast. He fasts perpetually."The Messenger of Allah ﷺ then said, "He has not fasted who fasts forever."
حدثنا أبو النضر وحسن بن موسى قالا ثنا شيبان عن ليث عن شهر
أتي النبي ﷺ بشراب فدار على القوم وفيهم رجل صائم فلما بلغه قال له اشرب فقيل يا رسول الله إنه ليس يفطر ويصوم الدهر فقال يعني رسول الله ﷺ لا صام من صام الأبد
No references are available.
Its isnad is hasan, it was mentioned previously at 22437 in similar wording.