Prohibition of Fasting for a lifetime for the one who will be harmed by that or who will neglect other duties, or does not break his fast on the two 'Ids or during the days of At-Tashriq; It is better to fast alternate days Sahih Muslim 1159 k

Sahih Muslim 1159k
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Translation
'Abdullah b. 'Amr (Allah be pleased with both of them) reported Allah's Messenger (ﷺ) as saying

With Allah the best fasting is that of David and the best prayer is that of David (peace be upon him) for he slept half of the night and stood for prayer for the third of it and (then) slept the sixth part of it and he observed fast one day and broke on the other.