Sayyiduna Ibn Umar (may Allah be pleased with them both) said that when the Messenger of Allah (peace and blessings be upon him) was at al-Mu'arras of Dhu al-Hulayfah, inside the valley, someone came to him (peace and blessings be upon him) and it was said: "You are in a blessed plain."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 13115