Sayyiduna Mu'adh bin Jabal (may Allah be pleased with him) narrates from the Prophet (peace and blessings be upon him) that he (peace and blessings be upon him) said: "The excellence of prayer in congregation over a man's prayer alone is twenty-five times."
Hadith Referenceالمعجم الكبير للطبراني / باب الميم / 17419