What is the ruling on the the Imam ordering a worshipper to leave the first row and go back to the second row so that the second row may be completed?

Many scholars are of the opinion that a person praying alone behind the صف (row) may pull someone from the row in front of him to stand with him, so that his prayer does not become invalid according to those who hold that view. Accordingly, the aforementioned Imam was correct in what he did. The majority of scholars hold the view that his prayer is valid in this case.