1 Peter 3:16

Having a good conscience
Meaning not the faculty of the conscience itself, which is naturally evil, and defiled with sin, and is only made good by the sanctification of the Spirit, and the sprinkling of the blood of Jesus, by which the heart is sprinkled from it, and that itself purged from dead works; but a life and conversation according to the dictates of such a conscience, in the uprightness and sincerity of it, and by the grace of God, and according to the Gospel, and whereby the doctrines of it are adorned; for, as besides internal sanctification of God, or a fearing of him, and believing in him with the heart, there must be a profession of him with the mouth, and a reason of faith and hope given verbally, when there is an occasion for it; so to both must be added a conscientious discharge of duty, both to God and men, which is one way of defending and recommending the doctrines of the Gospel:

that whereas they speak evil of you as of evildoers;
as vain, proud, haughty, and arrogant persons, as seditious men, enemies to order and civil magistracy; as such that speak evil of dignities, and despise government; when they shall see your modest and humble deportment in the world, and before them, and with what reverence and esteem you treat them:

they may be ashamed that falsely accuse your good conversation in
Christ;
which was in consequence of their being in Christ, and made new creatures by him, and was as became his Gospel, and by and under the influence of his grace and Spirit.