having a good conscience; that, wherein ye are spoken against, they may be put to shame who revile your good manner of life in Christ.

Being conscious that you have done no wrong; so that those who say evil things about your good way of life as Christians may be put to shame.

εχοντες συνειδησιν αγαθην, ινα, ενω σας καταλαλωσιν ως κακοποιους, καταισχυνθωσιν οι συκοφαντουντες την καλην σας εν Χριστω διαγωγην.

Having a good conscience; that, whereas they speak evil of you, as of evildoers, they may be ashamed that falsely accuse your good conversation in Christ.