Ata ibn Yasar عطاء بن يسار أبو محمد مولى ميمونة · The Book of Fasting

"The Messenger of Allah said to me: 'O 'Abdullah bin 'Amr, you fast all the time and you do stand (in prayer) at night, but if you do that your eyes will become sunken and you will become exhausted. There is no fast for one who fasts every day of his life. Fasting a lifetime means fasting three days each month,