Sahih Muslim Book 4, Hadith Number 1358.

Chapter : Desirability of observing the morning prayer at earlier hour and that is the time when there is darkness before dawn and the exposition about the length of recitation in it.

Abu Dharr reported: (The Messenger of Allah) said: How would you, or how would thou, act if you survive to live among people who defer prayer beyond the (prescribed) time? (The narrator said: Allah and His Messenger know best), whereupon he said: Observe prayer at its prescribed time, but if the Iqama is pronounced for (congregational) prayer, then observe prayer along with them. for herein is an excess of virtue.