Sahih Muslim Book 4, Hadith Number 1710.

Chapter : Preference for observing Nafl prayer in the house and permissibility of observing it in the mosque also.

‘Aisha reported that the Messenger of Allah (may peace be upon him) had a mat and he used it for making an apartment during the night and observed prayer in it, and the people began to pray with him, and he spread it (the mat) during the day time. The people crowded round him one night. He (the Holy Prophet) then said: O people, perform such acts as you are capable of doing, for Allah does not grow weary but you will get tired. The acts most pleasing to Allah are those which are done continuously, even if they are small. And it was the habit of the members of Muhammad’s (may peace be upon him) household that whenever they did an act they did it continuously.