Al-Harith bin Amr (may Allah be pleased with him) says: I came to the Prophet (peace and blessings be upon him) at Arafat or Mina, and the people had surrounded him (peace and blessings be upon him). The Bedouins came, and when they saw him (peace and blessings be upon him) they would say: "This is a blessed face." He mentioned a long hadith, and in it was also this: he (peace and blessings be upon him) appointed Yalamlam for the people of Yemen, to begin the talbiyah from there, and Dhat Irq for the people of Iraq, and the same for the people of the East as well.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الحج / 8919