Changing One’s Niyyah During the Prayer
Changing one’s niyyah during the prayer (after beginning it) is an important topic that has been clarified by Ibn Uthaimeen in ash-Sharh al-Mumti’ (vol. 2, 296-298) and in his Majmoo’ Fatawa (vol. 12). Here is the summary;:
Changing one’s intention from a non-specific optional prayer (نفل مطلق) to another non-specific optional prayer – this pray is valid, if such a scenario is conceivable. A non-specific optional prayer is prayed anytime during the day or night whenever one wishes (though not during forbidden periods).
Changing one’s intention from a non-specific optional prayer to a Specified Prayer (فرض معين أو نفل معين). Example: Changing one’s intention during a non-specific optional prayer to the Fard of Dhuhr. The Dhuhr here is invalid because the niyyah for it must be made before the opening takbeer for it to be valid.
Changing one’s intention from one Specified Prayer to another Specified Prayer is invalid. First example: A man is praying ‘Asr, then whilst praying he remembers that when praying Dhuhr earlier, he did not have Wudoo so he changes his niyyah from ‘Asr to Dhuhr to make up the Dhuhr. In this case both his ‘Asr and the Dhuhr are invalidated. Second example: A man is praying the two Sunnah for ‘Ishaa and during the prayer decides to change his niyyah to Witr. Here the Sunnah for ‘Ishaa has been invalidated and he is not even considered to have entered the Witr prayer. This is because the Sunnah of ‘Ishaa is a specified prayer and the Witr is likewise a specified prayer which requires the niyyah to be established before the opening takbeer.
Changing one’s intention from a Specified Prayer to a non-specific optional prayer is permitted and the prayer is sound. This is because a Specific Prayer has in reality two intentions: one for entering the prayer generally and another for that specific prayer. So if a person invalidates the niyyah for the Specific Prayer, the niyyah for general prayer remains (so long as he does not leave the prayer). For example a man enters the Dhuhr prayer with the niyyah for Dhuhr – he then cancels his niyyah for Dhuhr and continues praying, so what remains is his niyyah for the general prayer.