1 Peter 2:12

12 Keep your behavior excellent among the Gentiles, so that in the thing in which they slander you as evildoers, they may because of your good deeds, as they observe them, glorify God in the day of visitation.

Here Peter goes beyond his appeal to keep the thought life pure; he encourages them to have an excellent behavior while around Gentiles (unbelievers). The Greek word here for excellent behavior has the meaning of being virtuous, good, and honest.

During that time, under Nero, Christians were falsely accused of many evils. Peter wants them, in their good behavior, to remove any of those notions. Instead, they are to be known for good deeds, which will help to bring the unbeliever to believing faith, and therefore bring glory to God.