The traveler who joins the congregation in the third rak'ah and intends to shorten the prayer

Question:
Honorable Shaykh, if a person is traveling and joins a congregation that is in the third rak'ah, is it permissible for him to intend to shorten the prayer and conclude it with them?

Answer:
No, if the imam is completing the prayer, it is obligatory for the believer to complete the prayer, even if he is traveling. The Messenger (peace and blessings be upon him) said: This is also the practice of the Companions; when they prayed behind someone who completed the prayer, they completed it. Ibn Mas'ud and other Companions (may Allah be pleased with them) prayed behind 'Umar ibn al-Khattab (may Allah be pleased with him) in Mina, and 'Umar (may Allah be pleased with him) completed the prayer, so they completed it. This is the practice of the Companions. Yes.