SHAFAQNA – Imam Sadeq (AS) narrated that Allah (SWT) sent a revelation to Prophet Dawood (AS): O’ Dawood, whenever my believing servant commits a sin, and then leaves it and repents, and since he/she becomes embarrassed when remembers that sin, I (God) will forgive him/her, and will remove that sin from the memory of his/her protecting angels; and change that sin into good and reward; and have no fear of doing so; and I am the kindest .
Sheikh Sadooq also narrated from Imam Sadeq (AS) who said: Whoever commits a big or small sin and does not consider/believe that I (God) can punish him/her, or forgive him/her, I will never forgive him/her for that sin. And whoever commits a big or small sin and believes that I (God) can punish him/her, or forgive him/her, I will forgive him/her .
 Sokhane Khoda, Ayatollah Seyyed Hassan Shirazi, Page 84.
 As Above.