The implication clearly is that the slave has done nothing deserving a reprimand and/or a beating. The term “good” has also appeared in 1 Peter 2:12 and 1 Peter 2:14–15. In those verses it refers to “honorable” conduct and to obedience to the law of the land, that is, what is socially acceptable. In the present verse the reference to a “godly conscience” in 1 Peter 2:19 indicates that Peter has obedience to the Lord in view.
20 For what credit is it if, when you sin and are beaten for it, you endure? But if when you do good and suffer for it you endure, this is a gracious thing in the sight of God.