Sunan Abu Dawud
2360
Sahih+3

Narrated Ibn 'Umar:The Messenger of Allah (ﷺ) prohibited perpetual fasting. They (the people) said: You keep perpetual fasting, Messenger of Allah. He said: My position is not like that you yours. I am provided with food and drink

SahihAl-Albani
SahihMuhammad Muhyi Al-Din Abdul Hamid