Under Which Circumstances May One Invalidate the Prayer?

Under which circumstances may one invalidate the prayer?

It is haram to leave prayer unfinished without an excuse. However, it may be wajib (obligatory), mubah (allowed), or mustahab (desirable) to leave prayer unfinished in come cases. It is wajib for a person to leave a prayer unfinished if somebody’s life is under risk; for example, if a person who is being attacked or falls into fire or water asks for help. It is mubah to leave prayer unfinished in order to avoid a good from being destroyed or stolen. On the other hand, it is mustahab (desirable) for a person to leave prayer unfinished while he is establishing it individually in order to catch the congregation to get reward of establishing prayer in congregation (Ibn Abidin, Radd al-Muhtar, II, 504-505).

Source: Presidency Of Religious Affairs The Turkey, High Board of Religious Affairs FATWAS