One who enters the mosque for the 'Isha' prayer and remembers that he did not pray the Maghrib
Machine translationRead the Arabic original
Question:
This questioner sent a set of questions. He says: A person entered the mosque for the 'Isha' prayer, then he remembered that he had not prayed the Maghrib. What should he do?
Answer:
He is required to pray the Maghrib first, then join the remaining part of the 'Isha' prayer if he catches any of it. If he joined them with the intention of Maghrib, and the imam stands for the fourth rak'ah, he sits for the final tashahhud. Then, if he wishes, he says the taslim for himself, or if he wishes, he waits for the imam and says the taslim with him. That is permissible. Yes.
This questioner sent a set of questions. He says: A person entered the mosque for the 'Isha' prayer, then he remembered that he had not prayed the Maghrib. What should he do?
Answer:
He is required to pray the Maghrib first, then join the remaining part of the 'Isha' prayer if he catches any of it. If he joined them with the intention of Maghrib, and the imam stands for the fourth rak'ah, he sits for the final tashahhud. Then, if he wishes, he says the taslim for himself, or if he wishes, he waits for the imam and says the taslim with him. That is permissible. Yes.
Source
نور على الدرب - الفوزان - 02/183 — archive.org (8:11)
The Arabic text is a machine transcription of the audio recording.