It is narrated from Hazrat Abu Hurairah (may Allah be pleased with him) that the Noble Prophet (peace and blessings be upon him) said: The superiority of prayer offered in congregation over prayer offered alone is twenty-five degrees more.
Hadith Referenceمسند احمد / مسند المكثرين من الصحابة / 9150
Hadith Gradingحکم دارالسلام:حديث صحيح، وهذا إسناد حسن، خ: 648، 649