Sunan an-Nasa'i

It was narrated from Mutarrif bin 'Abdullah bin 'Abdullah bin Ash-Shikhkhir: "My father told me that he heard the Messenger of Allah (ﷺ) say, when mention was made in his presence of a man who fasted for the rest of his life: 'He neither fasted nor broke his fast."' 'Ata said: "someone who heard him told me that Ibn 'Umar (said) that the Prophet (ﷺ) said: 'Whoever fasts every day of his life, then he has not fasted."