The ruling on a traveler praying behind a resident imam

Question:
May Allah reward you. Honorable Shaykh, a traveler entered with a group and prayed two rak'ahs with the intention of shortening the prayer, but he did not know whether the imam was a resident or a traveler. Is his prayer valid?

Answer:
They were careful and did not shorten, and he prayed with them shortening, while on the road, and he did not know whether this imam was a resident or a traveler, so he intended to shorten. They prayed two rak'ahs, so he prayed two rak'ahs with them and said the closing salam with them, and he did not know whether this imam was a resident or a traveler? And they are in a place of travel. Not on the road, but on the road. This is an indication of travel; this is an indication that he is a traveler. Yes. And if it becomes clear to you and your companion that this imam is a resident, he must make up the prayer. It is forbidden to say the closing salam. A person whose stay has become long, a person who realizes it immediately, must make up the prayer. I say, is it like now or later that he is a resident? He prays four rak'ahs.