Is it permissible to change the intention during prayer?
Machine translationRead the Arabic original
The questioner : A man intended to pray Maghrib, but he wants to switch from the Maghrib prayer to the 'Isha' prayer, the same prayer he was praying?
The Shaykh : No, no, it is valid.
The questioner : Okay, what if it is from a voluntary prayer to a difference?
The Shaykh : It is not valid.
The questioner : Okay, from an obligatory prayer to a voluntary one.
The Shaykh : If the voluntary prayer is specific, it is not valid, just as if he wanted to switch from an obligatory prayer to the witr, for example,
The Shaykh : No, no, it is valid.
The questioner : Okay, what if it is from a voluntary prayer to a difference?
The Shaykh : It is not valid.
The questioner : Okay, from an obligatory prayer to a voluntary one.
The Shaykh : If the voluntary prayer is specific, it is not valid, just as if he wanted to switch from an obligatory prayer to the witr, for example,
Source
قناة «فضيلة الشيخ محمد بن صالح العثيمين»، 361- هل يجوز تغيير النية في الصلاة /سؤال على الهاتف 📞 /ابن عثيمين — youtube.com
The Arabic text is a machine transcription of the audio recording.