Is the prayer valid for one who stands alone behind the rows due to lack of space?

Question:
Honorable Shaykh, may Allah grant you success. This questioner says: A man entered the mosque while the people were praying, and he did not find a place for himself in the row, so he stood behind them alone. Is his prayer valid?

Answer:
If someone comes and stands with him, his prayer is valid, but if he continues [praying alone], his prayer is not valid. The Prophet , so he said, "There is no prayer for a single person behind the rows." Yes.