Ruling on the traveler praying behind the resident

Question:
Is it permissible for a traveler to pray the Dhuhr prayer in full if he encounters a congregation of residents, and to shorten the Asr prayer to its time? And the reverse: if he encounters a congregation for the Asr prayer while he is a traveler, and he has not prayed Dhuhr, does he shorten Dhuhr and pray four rak'ahs?

Answer:
If a traveler catches up with the residents, he prays four rak'ahs with them. If he prays alone, he prays two rak'ahs. If he catches up with them while they are praying Asr, and he has not prayed Dhuhr, he prays Asr with them with the intention of Dhuhr, four rak'ahs. Then, when they conclude the prayer, he stands up and prays Asr, two rak'ahs.

Question: How do you mean "Asr with the intention of Dhuhr"?

Answer: He prays Dhuhr behind those who are praying Asr. There is no harm in this, according to the correct view, because it is in agreement with it. The intention is the intention of... if he intends the Dhuhr that is obligatory upon him, and prays it behind those who are praying Asr, then after they conclude the prayer, he prays the Asr that is obligatory upon him, two rak'ahs.
So the conclusion: That a traveler, if he prays with the residents, prays four rak'ahs, and if he prays alone, or with travelers, prays two rak'ahs. Ibn Abbas was asked, and it was said to him: "O Abu al-Abbas, why is it that when we pray with the imam we pray four rak'ahs, and when we pray alone we pray two rak'ahs?" Ibn Abbas said: "This is the Sunnah."
So the Sunnah for a traveler, if he prays with a resident, is to pray four rak'ahs, and if he prays alone, or with travelers, to pray two rak'ahs.