The Sunnah at আরাফাত is to combine Dhuhr and Asr সালাতs at the time of Dhuhr (early combination, or jam' taqdim). Both সালাতs are shortened to 2 rak'ahs each since the হাজী is considered a traveler. নবী করীম (সাল্লাল্লাহু আলাইহি ওয়া সাল্লাম) performed them with one adhan and two iqamas — meaning one call to সালাত is given, then Dhuhr is prayed with its own iqama, followed immediately by Asr with its own iqama. No voluntary সালাতs (Sunnah সালাতs) are prayed between them.
This combining serves an important practical purpose: it frees up the entire afternoon from after the সালাতs until sunset for uninterrupted dua, dhikr, and worship — the core purpose of the Day of আরাফাত. The afternoon hours are the most precious time of the entire হজ্জ and should not be interrupted by waiting for the Asr সালাত time.
Regarding who should combine: the majority of scholars say all হাজীগণ at আরাফাত combine, even residents of মক্কা মুকাররমা who are not technically travelers. The combining is specifically linked to the হজ্জ ritual at আরাফাত, not just to the traveler's concession. The same principle applies at মুযদালিফা, where Maghrib and Isha are combined at Isha time (jam' ta'khir — delayed combination). After the combined সালাত at আরাফাত, face the Qiblah, raise your hands, and dedicate yourself fully to দোয়া.