What does one do if he enters the mosque and finds the row full?

Question:
The listeners, 'Amad Amin al-Dad and Subhi 'Abd al-Karim Ma'raj from Syria, sent a question asking about the prayer of a person praying alone behind the row. If a person enters and finds the row full, is it prescribed for him to pray, or what is his situation?
May Allah reward you with good.

Answer:
What is prescribed for him is that he remains until he finds a gap, meaning: he should look for a gap in the row until he can enter it, or stand with the imam on his right if that is possible. Otherwise, let him remain and not pray alone, in case he finds one of the new entrants to the congregation to pray with him. He should not pray alone; if he prays alone, his prayer is not valid. He must either find a gap, being patient and not rushing until he finds one, or stand with the imam on his right. If he does not find a place despite his effort, he should wait in case someone comes to stand with him. If they pray and no one comes, he prays alone. The Prophet (peace and blessings be upon him) said: And when he saw a man who had prayed alone behind the row, he ordered him to repeat it. He saw a man who had prayed behind the row alone, so he ordered him to repeat the prayer. And when Abu Bakrah bowed down behind the row, he forbade him and said: .
So, one should not bow down behind the row and then walk to the row, nor should he pray alone behind the row, but rather on the imam's right, or look for a gap in case he finds one to enter the row. If that is difficult for him after his effort, he should wait, and he should not pull anyone either. Yes.