Ibn-e Mas'ood was one of the scribers of revelation.  He was constantly
scribing whatever was being revealed of the Holy Qur'an.

One day, the Prophet (pbuh&hf) asked him:  "Please read me some Quran'."

Ibn-e Mas'ood opened his Qur'an and read upto 4:41.  The Prophet (pbuh&hf)
was listening to it attentively.
"How will that time be, when we call a witness from each nation, and will
birng you as a witness unto this nation" (4:41)

The eyes of the Prophet (pbuh&hf) overfolwed with tears, and asked of
Ibn-e Mas'ood:  "That is enough."  (1)

(1)  Kahl al-Basar, Muhaddith Qummi, p. 79