It is narrated from Sayyiduna Ibn Umar (may Allah be pleased with them both) that the Messenger of Allah (peace and blessings be upon him) said: "The superiority of prayer performed in congregation over prayer performed alone is twenty-seven degrees."
Hadith Referenceمسند احمد / مسند المكثرين من الصحابة / 5332
Hadith Gradingحکم دارالسلام:إسناده صحيح ، خ : 645، م : 650.