Abdullah ibn Masud R.A attained such a knowledge of the Quran that he would say, "By Him besides Whom there is no god, no verse of the book of God has been revealed without my knowing where it was revealed and the circumstances of its revelation. By God, if I know there was anyone who knew more of the Book of Allah, I will do whatever is in my power to be with him."
Abdullah R.A was not exaggerating in what he said about himself. Once Amirul mu'mineen, Umar ibn al-Khattab R.A met a caravan on one of his journeys as caliph. It was pitch dark and the caravan could not be seen properly. Umar R.A ordered someone to hail the caravan. It happened that Abdullah ibn Masud was in it.
"From where do you come?" asked Umar.
"From a deep valley," came the reply. (The expression used fajj amiq deep valley--is a Quranic one).
"And where are you going?" asked Umar.
"To the ancient house," came the reply. (The expression used al-bayt al-atiq ancient house, is a Quranic one.)
"There is a learned person (Alim) among them," said Umar and he commanded someone to ask the person:
"Which part of the Quran is the greatest?"
"God. There is no god except Him, the Living, the Self-subsisting. Neither slumber overtakes Him nor sleep," replied the person answering, quoting the Ayat al-Kursi (the verse of the Throne).
"Which part of the Quran is the most clear on justice?"
"God commands what it just and fair the feeding of relatives..." came the answer.
"What it the most comprehensive statement of the Quran?'
"Whoever does an atom's weight of good shall see it, and whoever does an atom's weight of evil shall see it."
"Which part of the Quran gives risk to the greatest hope?'
"Say, O my servants who have wasted their resources, do not despair of the mercy of God. Indeed, God forgives all sins. He is the Forgiving, the Compassionate."
Thereupon Umar asked:
"Is Abdullah ibn Masud among you?'
"Yes, by God," the men in the caravan replied.
