Do not let your adorning be external—the braiding of hair and the putting on of gold jewelry, or the clothing you wear—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. 1 Peter 3:3-4
Another quote from John Piper found in his sermon,The Beautiful Faith of Fearless Submission:
We know this does not mean that all jewelry and all hair styling is excluded because then all clothing would be excluded as well, because it says, “Don’t let your adorning be external . . . the clothing you wear.” What he means is: Don’t focus your main attention and effort on how you look on the outside; focus it on the beauty that is inside. Exert more effort and be more concerned with inner beauty than outer beauty.
And he is specific in verse 4. When a woman puts her hope in God and not her husband and not in her looks, and when she overcomes fear by the promises of God, this will have an effect on her heart: It will give her an inner tranquility. That’s what Peter means in verse 4 by “the imperishable beauty of a gentle and quiet spirit, which in God’s sight is very precious.