Ruling on the congregational prayer for the traveler

A confused listener (H. M.) asks about praying individually or in congregation in a town, and about leaving the congregation, specifically regarding the traveler. She says: A man traveled from one town to another and arrived in the town before the midday prayer. When the call to prayer was made, he did not pray, intending to combine the afternoon and midday prayers, and he stayed in the town. When the call for the afternoon prayer was made, he combined the two prayers while in the town. After the prayer, he went to his home town. Is his prayer valid? Please inform us, may Allah reward you with every good.
Answer: The prayer is valid, if Allah wills, but he made a mistake and did wrong when he prayed alone. It was obligatory for him to pray with the people when he arrived in the town, and he should not have prayed alone, because the congregation is an individual obligation. So it is obligatory for one who arrives in a town and is alone to pray with the people and complete four rak'ahs. If he came from a distant town that is considered a journey, he prays four rak'ahs with the people and it is not permissible for him to pray alone. However, if he missed the prayer with the people, he prays alone two rak'ahs, if he came from a distant town where his journey from it is considered a legal journey. As for him praying alone, it is not permissible; rather, it is obligatory for him to pray with the congregation and complete four rak'ahs. But if he was with two brothers or more and they prayed two rak'ahs and combined, there is no blame on them. Yes.