This phrase is a variation of the concept Peter had referenced a number of times previously, namely, honourable conduct (1 Peter 2:12), good deeds (1 Peter 2:12), doing good (1 Peter 2:15, 1 Peter 2:20; 1 Peter 3:6, 1 Peter 3:13, 1 Peter 3:17), respectful and pure conduct (1 Peter 3:2). It is a form of behaviour rooted “in Christ” because one is born again through his resurrection to a living hope (1 Peter 1:3–4).
16 having a good conscience, so that, when you are slandered, those who revile your good behavior in Christ may be put to shame.