Sahih Bukhari
Call to Prayers (Adhaan)
Volume: 001 / Book Number: 011 / Hadith Number: 623
Narrated Abu Musa:
The Prophet said, "The people who get tremendous reward for the prayer are those who are farthest away (from the mosque) and then those who are next farthest and so on. Similarly one who waits to pray with the Imam has greater reward than one who prays and goes to bed. "