Sayyiduna Ibn Abbas (may Allah be pleased with them both) narrates that the Messenger of Allah (peace and blessings be upon him) said: "When going to Arafat, go beyond the valley of ‘Urnah, and (when coming to Muzdalifah) hasten past the valley of Muhassir."
Hadith Referenceصحيح ابن خزيمه / جماع أبواب ذكر أفعال اختلف الناس فى إباحته للمحرم، نصت سنة النبى صلى الله عليه وسلم أو دلت على إباحتها / 2816
Sayyiduna Ibn Abbas (may Allah be pleased with them both) narrates that it used to be said: "Go beyond the Valley of Muhassir and the Valley of 'Aranah." The meaning of 'Aranah is that you should not stay in the Valley of 'Arafah, and the prohibition regarding the Valley of Muhassir means that when staying in Muzdalifah, do not stop in the Valley of Muhassir; rather, leave it and stay ahead.
Hadith Referenceصحيح ابن خزيمه / جماع أبواب ذكر أفعال اختلف الناس فى إباحته للمحرم، نصت سنة النبى صلى الله عليه وسلم أو دلت على إباحتها / 2817