Sayyiduna Umar bin al-Khattab (may Allah be pleased with him) said: The Messenger of Allah (peace and blessings be upon him) told me that when he (peace and blessings be upon him) was at al-Aqiq: "A visitor came to me from my Lord and said: Pray in this blessed valley. And he said: 'Umratun fi hajjah' (an Umrah within a Hajj)."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الحج / 8848