How can one benefit from the dispensation of shortening prayers while traveling if attending congregational prayer is obligatory during travel and the imam of the mosque is a resident, which means completing the prayer and not benefiting from the dispensation?

If a traveler prays behind a resident, he must pray the full prayer, as was narrated from Ibn Abbas, may Allah be pleased with them both, that it is the Sunnah of the Prophet, peace and blessings be upon him, and the Companions completed their prayers behind Uthman for this reason.

Many scholars have gone to the opinion that congregational prayer is obligatory for the traveler, due to the general evidence for the obligation of congregational prayer, and the saying of the Prophet, peace and blessings be upon him: "Whoever hears the call to prayer and does not respond to it, there is no prayer for him except for an excuse," and the saying of Ibn Mas'ud, may Allah be pleased with him: "Whoever wishes to meet Allah tomorrow as a Muslim, let him observe these prayers wherever the call to them is made." Therefore, it is obligatory for every Muslim, traveler or resident, to pray in congregation, and to beware of praying alone if he hears the call to prayer.

Accordingly, a traveler can shorten the prayer in several cases, including: if he misses the congregation due to an excuse, or prays with other travelers, or if he combines two prayers by advancing or delaying them, then he shortens the prayer that he does not pray with the Imam. Also, if he believes that congregational prayer is not obligatory during travel or he imitates someone who gives a fatwa to that effect. It is better to pray in congregation even with the opinion that congregational prayer is not obligatory during travel, in order to gain the reward of the congregation and to avoid the difference of opinion of those who made it obligatory.