It is transmitted from Sayyiduna Ka'b bin Ujrah (may Allah be pleased with him) that the Prophet (peace and blessings be upon him) prayed Maghrib in the mosque of Banu Abd al-Ashhal. When he (peace and blessings be upon him) finished the prayer, he saw those people offering voluntary prayers and said: "O people! This is the prayer of the houses." (That is, praying the voluntary prayers at home is better and more virtuous.)
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 3040