Must one make up [the fast] if one acted on the presumption that something was not a breaker of the fast, then it became clear to one that it was a breaker of the fast?

If it becomes clear to a Mujtahid that a certain action does not invalidate the fast, but then his ijtihad changes and he deems it to be an invalidator, he is not required to make up (the fast). Similarly, an ordinary person (layman) who follows a scholar he trusts, and then that scholar's fatwa changes, is not required to make up (the fast). This is because a later ijtihad does not nullify a previous ijtihad. Nullifying ijtihad with ijtihad would lead to instability in rulings. What has been reported from the Companions, such as Umar and Abu Bakr, supports this meaning.