1. Does licking clean fingers invalidate the fast inadvertently? 2. Is the fasting for expiation of an oath invalidated if water enters the mouth inadvertently after the dawn adhan, and is it obligatory to repeat it? 3. Does a fasting person break their fast if they continue eating or drinking after the dawn adhan due to ignorance of the ruling, and does that necessitate making up the fast?

Licking the fingers after eating is a Sunnah. If done without reason, it is a bad habit that does not invalidate the fast, provided the hand is clean.

As for intentionally swallowing water during the daytime while fasting, it invalidates the fast and incurs sin. Scholars have differed on whether it necessitates re-observing the expiation fast or merely making up that day. The more cautious approach is to re-observe it. According to the majority of scholars, it is not obligatory to refrain from eating and drinking for the rest of the day outside of Ramadan. However, if the water was swallowed due to forgetfulness, the fast is valid according to the majority.

The time to abstain from things that invalidate the fast is at the break of true dawn. Therefore, whoever eats after ascertaining the break of dawn or after an accurately timed Adhan, their fast is invalid and they must make it up, except for those excused by ignorance.

Some scholars are of the view that it is permissible to finish drinking from a vessel held in the hand upon hearing the Adhan of Fajr. Whoever follows this opinion without excessively seeking out dispensations, their fast is valid.