Yahya related to me from Malik from Zayd ibn Aslam from his
father that the Messenger of Allah, may Allah bless him and grant him
peace, was on one of his journeys, and one night Umar ibn al-Khattab,
who was travelling with him, asked him about something, but he did not
answer him. He asked him again, but he did not answer him. Then he
asked him again, and again he did not answer him. Umar said, "May your
mother be bereaved of you, Umar. Three times you have importuned the
Messenger of Allah, may Allah bless him and grant him peace, with a
question and he has not answered you at all."
Umar continued,
"I got my camel moving until, when I was in front of the people, I
feared that a piece of Qur'an was being sent down about me. It was not
long before I heard a crier calling for me, and I said that I feared
that a piece of Qur'an had been sent down about me." He continued, "I
came to the Messenger of Allah, may Allah bless him and grant him
peace, and said, 'Peace be upon you' to him, and he said, 'A sura has
been sent down to me this night that is more beloved to me than
anything on which the sun rises.' Then he recited al-Fath (Sura 48).
USC-MSA web (English) reference: Book 15, Hadith 9
Arabic reference: Book 15, Hadith 481