'Abdullah bin sa'd Radiyallahu 'Anhu says:
"I enquired from Rasulullah Sallallahu 'Alayhi Wasallam, is it more meritorious to perform nafil salaah in the home or in the masjid? Rasulullah Sallallahu 'Aayhi Wasallam replied: 'Do you observe that my house is so near the masjid (which does not make it difficult, or cause a hindrance in coming to the masjid, in spite of all this) I prefer to perform the salaah, besides the faraa-id, in my house, rather than in the masjid".
English reference: Book 41, Hadith 280
Arabic reference: Book 42, Hadith 297