Hadith 4:4
Waki’ narrated to us, from Nasr ibn Yahya, from ‘Ikrimah, from Nasr ibn Shayban, who said: I asked Abu Salamah ibn ‘Abd al-Rahman, and he mentioned from his father, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "Whoever fasts it out of faith and seeking reward, his past sins will be forgiven for him."
حدثنا وكيع عن نصر بن يحيى عن عكرمة عن نصر بن شيبان قال سألت أبا سلمة بن عبد الرحمن فذكر عن أبيه قال قال رسول الله صلى الله عليه وسلم من صامه ايمانا واحتسابا غفر له ما تقدم من ذنبه