Sahih Muslim Book 4, Hadith Number 1713.

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

‘Aisha reported Allah’s Messenger (may peace be upon him) as saying: The acts most pleasing to Allah are those which are done continuously, even if they are small. and when ‘Aisha did any act she did it continuously.