Abu Hurairah (RA) said: The Messenger of Allah (ﷺ) used to say in prostration:

اَللَّهُمَّ اغْفِرْ لِي ذَنْبِيْ كُلَّهُ دِقَّهُ وَجِلَّهُ، وَأَوَّلَهُ وَآخِرَهُ، وَعَلَانِيَّتَهُ وَسِرَّهُ

Allahum-maghfir lee dhanbee kullahu, diqqahu wa jillahu, wa 'awwalahu wa 'aakhirahu wa 'alaa-niyyatahu 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: 483