The Book Pertaining to the Merits of the Companions (Allah Be Pleased With Them) of the Holy Prophet (May Peace Be Upon Him) (Kitab Al-Fada'il Al-Sahabah)
Muslim :: Book 31 : Hadith 6019
Abu Ishaq reported that he heard Abu'l-Ahwas say: I was along with Abu Musa and Abu Mas'ud as Ibn Mas'ud died and one of them said to the other: Do you find one like him besides him? Thereupon he said: Do you say this (no one can be his rival)? He was admitted (to the company of the Holy Prophet) whereas we were detained and he had been present in the company of Allah's Messenger (may peace be upon him) whereas we had been absent.