How to pray Maghrib behind an imam who is praying 'Isha. (And is this situation considered a deviation from the imam?)

The questioner : All right, if the imam combined Maghrib and 'Isha for an excuse, for example, rain.

The Shaykh : Yes, exactly.

The questioner : And a man came, whether he knew or did not know that it was the 'Isha prayer, and he had not prayed Maghrib, so how does he act?

The Shaykh : He prays Maghrib behind the one who is praying 'Isha.

The questioner : Four rak'ahs, and the imam is praying, what does he do?

The Shaykh : No, he prays, he prays three.

The questioner : Then.

The Shaykh : That is, here we assume the situation is that he arrived and the 'Isha prayer had already been called for.

The questioner: Yes.

The Shaykh : So he caught the 'Isha prayer from its beginning, so it is not permissible for him to pray 'Isha while he has not yet prayed Maghrib, so he must follow this imam who is praying 'Isha, but he intends the Maghrib prayer, because Just as it is not permissible for a Muslim usually to advance or delay a prayer, so it is not permissible, even if he follows an imam who is praying the 'Isha prayer, for him to pray 'Isha and then repeat by praying the Maghrib prayer; rather, he begins the prayer as Maghrib behind this imam who is praying the 'Isha prayer. And we assumed that he followed the imam at the beginning of the prayer, so if the imam stands for the fourth rak'ah, he sits and intends to separate, he intends to separate from the imam, because adding to the three rak'ahs of the Maghrib prayer intentionally and deliberately invalidates it, like one who prayed Fajr four or three, or prayed 'Isha or Zuhr or 'Asr three or two; there is no difference in all these cases in the invalidation of the prayer by addition or subtraction. For this reason, he has an exit: to intend to separate from the imam, because he is compelled to perform the three rak'ahs of Maghrib and not follow him in the fourth. So if he says the taslim, he stands and follows the imam where he is, resuming the 'Isha prayer with him behind the imam, even if he catches him before the taslim. This is what...

The questioner : What happens in deviating from the Shaykh, if he says the taslim before the imam, but this intention of separation, how...

The Shaykh : He is compelled, he is compelled; this deviation is necessary, because which of the two deviations is the one whose doer is more excused? Is it that Ansari who entered following behind Mu'adh ibn Jabal (may Allah be pleased with him) while he was praying the 'Isha prayer with his people, so when he began Surat al-Baqarah, he cut off the prayer and turned away to pray alone? Which of the two men is more excused, this one or the one we mentioned just now? There is no doubt that the first is more excused, because he wants to make valid the prayer that Allah obligated upon him, which is three, not four. And it is not an excuse to reverse the timing prescribed by the Shari'ah, to intend to pray behind the imam four rak'ahs and then pray Maghrib. And we know that some say he intends a voluntary prayer behind this imam, praying four rak'ahs with the imam but intending it as voluntary, and then afterwards he resumes the prayer in the known order, praying three rak'ahs of Maghrib and then four rak'ahs of 'Isha. But here he falls into another deviation, and I do not know how one who issues this last fatwa does not notice it, which is his saying (peace and blessings be upon him): So it is not permissible for a person to pray a voluntary prayer while the people are praying an obligatory prayer. There is no doubt that all these cases contain a deviation, none is free from deviation. But the truth, as they say, is: "Some evil is less than some." And as the jurists say, "If a Muslim falls between two evils, or let us say now between two deviations, and he must choose one of them, let him choose the lighter of them." And this is part of the fiqh that a student of knowledge should know.

The questioner : But it appears, our Shaykh, that the last situation is lighter?

The Shaykh : Which one?

The questioner : That he prays with the intention of voluntary rather than obligatory, meaning he prays 'Isha with it. In the first situation, he did not pray 'Isha, he prayed Maghrib.

The Shaykh : But he did not pray the obligatory one.

The questioner : But the first one prayed the obligatory one, the obligatory 'Isha, then...

The Shaykh : No problem, I said the deviation is necessary, but now we are discussing which of the two deviations is less. The one who prayed Maghrib behind the one praying 'Isha, it is valid that he prayed an obligatory prayer, even if it is not that obligatory prayer in its form. For example, when the Messenger (peace and blessings be upon him) entered the Fajr prayer and saw a man praying the Sunnah of Fajr and the prayer had already been called for, he said to him: Because he added a voluntary prayer to the obligatory one. As for this one who is praying the three rak'ahs of the obligation, he has prayed an obligatory prayer, even if its form differs from that one. And for that reason we said that separation is necessary. Then, the principle of separation is also established in some other cases, so it mitigates the evil of the deviation in what we are dealing with.