اَللَّهُمَّ اغْفِرْ لِي ذَنْبِي كُلَّهُ، دِقَّهُ وَجِلَّهُ، وَأَوَّلَهُ وَآخِرَهُ، وَعَلَانِيَتَهُ وَسِرَّهُ
Transliteration
Allahummaghfir li dhanbi kullahu, diqqahu wa jillahu, wa awwalahu wa akhirahu, wa 'alaniyatahu wa sirrah
English meaning
O Allah, forgive me all of my sins — small and great, first and last, public and private.
When is it recited?
In prostration and outside of prayer.
Source
Muslim, Salat 216