I asked Ayesha about the fasting of the Messenger of Allah ﷺ. She replied, "As far as I know, he never fasted an entire month without breaking his fast on some of its days, nor did he leave a month without fasting on some of its days, until he passed away."
حدثنا وكيع حدثنا كهمس
سألت عائشة عن صوم رسول الله ﷺ قالت ما علمته صام شهرا حتى يفطر منه ولا أفطره حتى يصوم منه حتى مضى لسبيله
Its isnad is sahih. Kahmas is Ibn Hasan Tamimi, and he is trustworthy, his hadith being found in the collections of all six/major compilers. The hadith was narrated by Muslim, 1/809, no. 1156, and Nasai, 4/199, no. 2349, both in the chapter on fasting.