Show us the Greek word for penance and where it shows up in Scripture.
Repentance is in the Bible a lot. But God never commanded us to do penance. That’s another example of deliberate mistranslation by the Catholic church in order to support its heretical doctrine of works based salvation.
And of course, the Catholic church just happens to be the one to be able to dictate which works can save and to dish out penance for people to do to earn God’s forgiveness.
How convenient.
The Greek for either is "metanoia". "Do penance" better matches the works of John the Baptist who wore a hairshirt, lived a hermit, and ate meager foods, -- typical works of Catholic penance.