Is the prayer of one who caught the Imam while he was saying the Tasleem, and then completed his prayer, valid?

Scholars differ concerning the validity of a follower joining the Imam if the follower says the takbeer after the Imam has begun the first tasleem but before completing it:

- Some are of the opinion that the following is valid because the Imam has not yet completed the prayer, and the tasleem, in their view, is part of the prayer. - Others are of the opinion that the following is not valid because the Imam has begun to exit the prayer.

It is better for the follower not to join the Imam in this situation to avoid disagreement. However, if he does join, the preponderant opinion is that his prayer is valid.