The World Federation One Stop Fiqh

Ruling 743

If a person starts to perform prayers with the intention of the ẓuhr prayer and while performing it realises that he has already performed the ẓuhr prayer, he cannot change his intention to the ʿaṣr prayer. Instead, he must break his prayer and perform the ʿaṣr prayer. The same applies to maghrib and ʿishāʾ prayers.