Answered by Shaykh Abu Usamah
Answer:
Al-Salam `alaykum
A musafir must pray the full prayer when he is following an Imam who is not a traveller. The prayer that was offered full behind the Imam is valid and correct.
The following is from Anis al-Musafir:
“A musāfir can also follow an imām who is a muqīm as long as it is within the time of that salāh. If the time has expired then he can follow him for the Fajr and Maghrib salāhs and not for the Zuhr, ‛Asr, and ‛Ishā salāhs.”
In this case he must offer the full salāh behind the imām.