When he comes and the row is already complete

Ata says: If a man comes to the mosque for prayer and the row has been completed, then if he is able to enter the row, he should enter it. If that is not possible, he should take hold of a man and make him stand with him. He should not stand alone.

Amr bin Maymun says: I asked Ibrahim: "If I come for prayer and the row is already full, what should I do?" He said: "Make a man stand with you. If you pray alone, repeat the prayer."