If one remembers a missed prayer while praying the current obligatory prayer

The questioner:
If a person who forgot a prayer remembers it while performing the obligatory prayer that follows it, what should he do?

The Shaykh:
He should complete the prayer he is currently performing with the imam, then make up the missed prayer, and then the current one. Or, if it is easy for him to break off the prayer, he should break it off and pray the current one. He breaks off the current prayer and prays the missed one, then prays the current one. This is what is obligatory for him, just as the Prophet (peace and blessings be upon him) did on the day of the Battle of the Trench. When he was occupied and missed the 'Asr prayer, he prayed 'Asr, then Maghrib, then 'Isha'. So, if he has started 'Asr and then remembers that he did not pray Zuhr, he breaks off the prayer with the intention, he breaks off 'Asr, then he says the takbir anew with the intention of Zuhr,

The questioner:
May Allah preserve you.

The Shaykh:
and prays 'Asr.