‘Abdullah bin ‘Umar narrated: “A man came to the Prophet and said: ‘O Messenger of Allah! How many times should the servant be pardoned?’ The Prophet was silent. Then he said: ‘O Messenger of Allah! How many times should the servant be pardoned?’ He said: ‘ Seventy times each day.'”
Jami` at-Tirmidhi, Book 27, Hadith 55