The word “beauty” is not found in the Greek but is added in translation to convey the sense better. 1 Peter 3:3 had used the word “adorning” in reference to externalities. 1 Peter 3:4 has spoken about the “hidden,” that is, the internal “adorning.” Peter now adds that this hidden adorning has an “imperishable” quality. And since he had been talking about “adorning,” translators add the word “beauty” as an equivalent to “adorning” (which makes sense if you understand that braided hair, gold jewellery, and clothing were to be beautiful). But since Peter does not use the word “beauty,” we ought not to be sidetracked by the word; Peter’s emphasis lies on “imperishable,” in contrast to hair, jewellery, and clothing, which all pass away. It is the same word Peter had used in 1 Peter 1:4 to describe the inheritance Jesus obtained for us through his resurrection from the dead.
4 but let your adorning be the hidden person of the heart with the imperishable beauty of a gentle and quiet spirit, which in God’s sight is very precious.