What is the ruling on a person praying alone behind the rows? And what is the ruling on praying in rows that are far from the rows adjacent to the imam?

Abu Layla : I want to ask a question during the iqamah for the congregational prayer. Of course, many people are unaware of the ruling regarding who starts the row and who stands behind the imam. Sometimes, Shaykh, when the imam begins to bow, I see some of these people still lining up at the entrance, meaning where they stand in the row. Sometimes the row, for example, has some people with knowledge who lined up behind the imam, and that person is alone in a row, and he starts filling the row from here and there. What is the ruling on his prayer, Shaykh? Of course, if the prayer ended and he did not complete the row with him, or on both sides.

The Shaykh : Whose prayer?
Abu Layla : The one who lined up alone in the same line where he started filling, meaning he started from the end of the row and left a long distance between him and the others.

The Shaykh : I mean, can we say that he prayed alone? Because there is a difference between being alone and being two or three.
Abu Layla : Sometimes he is alone, and sometimes there are others with him.

The Shaykh : I am going to answer you: if he is alone, his prayer is invalid and he has to repeat the prayer; but if there are two or three here, and the congregation is behind the imam as I said, meaning the row starts from there, then their prayer is valid, but they are sinful in that they did not reach the row; is the difference clear?
Abu Layla : If he prayed alone, does he repeat the prayer?

The Shaykh : Of course, he repeats it.

The questioner : Okay, Shaykh, if a person comes and finds a person on the right of the row... he goes to line up with him so he does not pray alone.

The Shaykh : No, on the contrary, according to the Shari'ah, he lines up behind the imam.

The questioner : Behind the imam.

The Shaykh : After he tries to join the row in front of him, meaning, remove this image from your mind that he is standing on the right or the left, and visualize the image of a person who wants to pray and does not find anyone to pray with; what does he do? Some people say he should pull someone from the row; the hadith regarding pulling is weak and not authentic. So if he does not pull, but he tries to pull himself, he joins himself to the row; and in many cases in reality, a person finds a large gap in the row. If the row is contrary to custom and the Sunnah, meaning if the row is contrary to custom and the Sunnah, meaning it is tightly packed so that he does not find space to join, then he prays behind him alone behind the imam, and his prayer will be valid, because Allah does not burden a soul beyond its capacity. Here, if he finds a person on the right or on the left, it is not important; the important thing is that he does what is required of him.

The questioner : May Allah reward you with good.