Hazrat Imam Mohammed Baqir (a.s.) says. Whoever recites the following Dua thrice after finishing the prayer and without having moved, Allah will pardon all his sins even if these be as many as the foams of the sea.

ASTAGHFERUL LAAHAL LAZEE LAA ELAAHA ILLAA HOWAL HAYYUL QAYYOOMO ZUL JALAALE WAL IKRAAME WA ATOOBO ELAYHE.

I seek forgiveness of Allah Who, there is no deity other than He, the Ever-Living the Self-Subsistent the Glorious and the Gracious. I turn unto Him (repentant).