Musnad Ahmad 31:768

Ya'qub narrated to us, my father narrated to us, from Muhammad ibn Ishaq, Muhammad ibn Ibrahim ibn al-Harith al-Taymi narrated to us, from Abu Salamah ibn 'Abd al-Rahman ibn 'Awf and Abu Umamah ibn Sahl ibn Hunayf, from Abu Sa'id al-Khudri and Abu Hurayrah, who both said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "Whoever performs ghusl on Friday, uses the siwak, applies some perfume if he has any, and wears his best clothes, then goes out until he reaches the mosque, and does not step over the necks of the people, then prays as much as he wills to pray, then remains silent when the Imam comes out, and does not speak until he finishes his prayer, it will be an expiation for what is between it and the Friday that preceded it." He said: And Abu Hurayrah used to say: "And three days extra, for Allah has made the good deed worth ten times its like."