Sayyiduna Ya'la (may Allah be pleased with him) said: I said to Umar bin al-Khattab (may Allah be pleased with him): "I wish that I could see the Messenger of Allah (peace and blessings be upon him) at the time revelation is coming down upon him." He said: Then we were on a journey with the Messenger of Allah (peace and blessings be upon him); he (peace and blessings be upon him) stopped at a place, and a Bedouin came to him (peace and blessings be upon him) wearing a cloak (jubbah) smeared with saffron. He said: "O Messenger of Allah, I have entered ihram for Umrah, and the people are laughing at me, so what should I do?" The Messenger of Allah (peace and blessings be upon him) gave him no answer until Allah Almighty sent down revelation upon him (peace and blessings be upon him). Umar (may Allah be pleased with him) signalled to me with his hand, so I put my head into the tent, and I saw that the eyes and forehead of the Messenger of Allah (peace and blessings be upon him) were reddened. Then, when that state left him (peace and blessings be upon him), he said: "Where is the one who asked about Umrah?" The man said: "O Messenger of Allah, here I am." He (peace and blessings be upon him) said: "Take off your cloak, and whatever you used to do in your Hajj, do that in your Umrah."
Hadith Referenceالمعجم الكبير للطبراني / باب الياء / 18874