The ruling on a resident following a traveler in prayer

Question:
This is a letter from the questioner (A. M.) from Riyadh. He has two questions in his letter. In his first question, he asks: What is the ruling on a person who shortens his prayer following one who completes it, or the reverse? And how do they perform it?

Answer:
If a person who shortens his prayer follows one who completes it, then when the imam finishes his prayer of two rak'ahs, the resident stands up and completes four rak'ahs, if the imam is the traveler. He prays two rak'ahs, and then when he says the taslim, the people behind him who are residents and not travelers stand up and pray four rak'ahs, while the travelers say the taslim with him. This is if the imam is the traveler.
As for when the imam is the resident and the travelers are behind him, they complete the prayer with him, and they do not have the option to shorten it. Rather, they complete four rak'ahs with him, and they do not shorten the prayer behind one who completes four rak'ahs. This is based on what is established in the authentic hadith of Ibn 'Abbas (may Allah be pleased with them both), that he was asked about the one who prays behind the imam. They said to him: "O Abu al-'Abbas, why is it that when we pray behind the imam we pray four rak'ahs, and when we pray in our camps we pray two?" He said: "This is the Sunnah ." It was narrated by Imam Ahmad in his Musnad with a good chain of narration, and its original source is in Sahih Muslim.
This indicates that the prayer of the traveler behind the resident imam must be completed as four rak'ahs, due to the aforementioned hadith. And success is from Allah.