The Book of Prayers (Kitab Al-Salat)
Muslim :: Book 4 : Hadith 880
Abu Huraira reported: The Messenger of Allah (may peace be upon him) said: If you were to know, or if they were to know, what (excellence) lies in the first rows, there would have been drawing of lots (for filling them) ; and Ibn Harb said: For (occupying) the first row there would have been drawing of lots.