Sahih Muslim
The Book of Prayers (Kitab Al-Salat)
Book Number: 004 / Hadith Number: 1406
Jabir b. 'Abdullah narrated: Our houses were situated far away from the mosque; we, therefore, decided to sell our houses so that we may be able to come near the mosque. The Messenger of Allah (may peace be upon him) forbade us (to do so) and said: There is for every step (towards the mosque) a degree (of reward) for you.