Muslims fast the month of Ramadan because Allah has commanded them to do so. Therefore, Muslims worship Allah through fasting which is beloved to Allah and which He has enjoined upon us.

Allah singled out fasting for Himself from all other good deeds, because of its honoured status before Him, because He loves it and because it is a demonstration of sincerity towards Him, as it is a secret between a person and his Lord, which no one can see except Allah.

When a person becomes certain that the true dawn has come, he has to stop eating and drinking, and if there is food in his mouth he has to spit it out; if he does not do that, then he has invalidated his fast.

When the sun has set, it becomes permissible for the fasting person to break the fast, whether the muadhdhin has given the adhan or not. What counts is the setting of the sun.