Fiqh-us-Sunnah Volume 5, Hajj and ‘Umrah, Fiqh 5.099A.

According to the authentic ahadith the Prophet (peace be upon him) combined Zuhr and ‘Asr prayers while at Arafah. For this, azhan – call for the prayer – was given, then iqamah – the second call for prayer – was made. Then he offered Zuhr. After this, another iqamah was made and he offered ‘Asr prayer.

Al-Aswad and ‘Alqamah said: “For the completion of Hajj, Zuhr and ‘Asr prayers must be offered at Arafah in congregation behind an imam.”

Ibn Al-Munzhir said: “There is consensus among the scholars that the imam must combine Zuhr and ‘Asr prayers at Arafah, and so should any one offering prayer with the imam.” And in case one cannot combine these and pray behind an imam, one should combine them while praying alone.

It is reported that Ibn ‘Umar used to reside at Makkah, but when he went to Mina he would shorten his prayers. ‘Amr bin Dinar reported that Jabil bin Zaid told him: “Shorten your prayers at Arafah.” This is reported by Sa`id bin Mansur.