What should a worshiper do if someone next to them in congregational prayer leaves, according to the Shafi'is?

If there is only one person next to a worshiper in the row and that person leaves, it becomes disliked for the worshiper to remain alone behind the row. If he finds a gap in the row in front of him, he should move into it. If he does not find a gap, he may pull someone from the row in front of him, and it is recommended for that person to assist him. Nevertheless, if he completes his prayer alone, his prayer is valid. This is a summary of the Shafi'i madhhab.