Reference : Hisn al-Muslim 46

اللّهُـمَّ اغْفِـرْ لي ذَنْـبي كُلَّـه ، 
دِقَّـهُ وَجِلَّـه ، 
وَأَوَّلَـهُ وَآخِـرَه ، 
وَعَلانِيَّتَـهُ وَسِـرَّه
Allāhumma’ghfir lī dhanbī kullahu, 
diqqahu wa jillahu, 
wa awwalahu wa ākhirahu 
wa `alāniyyatahu wa sirrahu.


O Allah, forgive me all my sins, 
great and small, 
the first and the last, 
those that are apparent and those that are hidden.

Reference:
Muslim 1/350.

Chapter: While prostrating