Changing the Intention of a Voluntary Prayer and Converting It to an Obligatory One

The questioner:
May Allah forgive you, O Shaykh. Is it permissible to change the intention in voluntary prayers?

The Shaykh:
Sultan Yahya. I mean, a type who fasts two days or on a Thursday, and then remembers that he should make up the days he missed from Ramadan. I mean, after he had intended and it became morning. After he intended, it became morning. He makes it an obligatory fast, not a voluntary one. There is no issue with that. The bread from the night.

The questioner:
And what about the Sunnah prayer, for example?

The Shaykh:
It must be from the night. As for the prayer, if he intended it as a voluntary prayer and wants to make it an obligatory one, and whoever wishes to stop it, he starts the obligatory prayer from the beginning with Allahu Akbar. I mean, he exits the prayer. He exits the voluntary prayer and starts the obligatory one. He does not complete the voluntary prayer and then come to the obligatory one. And it is better to complete the voluntary prayer and then come to the obligatory one.