Sunan an-Nasa'i 2379
سنن النسائي#2379SahihIt was narrated that 'Imran said:"It was said: 'O Messenger of Allah, so and so never broke his fast, even for one day for the rest of his life.' He said: 'He has neither fasted nor broken his fast."" 'Ata said: "someone who heard him told me that Ibn 'Umar (said) that the Prophet said: 'Whoever fasts every day of his life, then he has not fasted
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Abu GhuddahSahih
Al-AlbaniSahih
Zubair Ali ZaiIsnaad Sahih
In-book reference: 22:290