If a traveler prays behind a resident, does he complete the prayer or shorten it?

The questioner : A traveling man prayed behind a resident who had already prayed two or three rak'ahs. Is it better for the traveler to shorten the prayer, or is it obligatory for him to complete it? And if he shortens it, how do I pray two or three rak'ahs? Come on, Sa'd, what is it?

The Shaykh : He prayed behind a resident who had already prayed two or three rak'ahs. What does that mean? Does it mean he missed two rak'ahs? Yes, he completes the prayer. If the traveler had only prayed two rak'ahs, he is now required to pray four.