Rules Regarding Things, which Invalidate a Fast
1662. If a person intentionally and voluntarily commits an act, which invalidates fast, his fast becomes void, but if he does not commit such an act intentionally, there is no objection in it. However, if a person in Janabat sleeps and the details which are mentioned in the rule no. 1640, does not do Ghusl till the Adhan for Fajr prayers, his fast will become void.