It is narrated from Sayyiduna Abu Ubaydah bin al-Jarrah (may Allah be pleased with him); he said: The Messenger of Allah (peace and blessings be upon him) said: "There is no prayer among the prayers more excellent than the Fajr prayer in congregation on Friday, and I do not think that whoever of you attends it will be anything but forgiven."
Hadith Referenceالمعجم الكبير للطبراني / العشرة / 363