Nafi' (may Allah have mercy on him) narrates from Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) that the Prophet (peace and blessings be upon him) fixed the course for the conditioned horses from al-Hafya' to Thaniyyat al-Wada', and fixed the course for the unconditioned horses from al-Thaniyyah to the mosque of Banu Zurayq.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب السبق والرمي / 19765