Sahih Muslim Book 4, Hadith Number 1359.

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’l-‘Aliyat al-Bara’ reported: I said to ‘Abdullah b. Samit: We say our Jumu’a prayer behind those rulers who defer the prayer. He (‘Abdullah b. Samit), struck my thigh that I felt pain and said: I asked Abu Dharr about it, he struck my thigh and said: I asked the Messenger of Allah (may peace be upon him) about it. Upon this he said: Observe prayer at its prescribed time, and treat prayer along with them (along with those Imams who deter prayer) as Nafl. ‘Abdullah said: It was narrated to me that the Messenger of Allah (may peace be upon him) struck the thigh of Abd Dharr.