Sayyiduna Ibn Abbas (may Allah be pleased with them both) said that the Messenger of Allah (peace and blessings be upon him) made the talbiyah for Hajj and arrived on the 4th of Dhul-Hijjah. He led us in the Fajr prayer in the valley of al-Batha', then said: "Whoever wishes to make it an Umrah, let him do so."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الحج / 8813