By "sexual purity," I mean the act of reserving sexual intimacy for marriage alone. When I say this, I'm not talking about abstinence born of fear of sexuality. Nor am I talking about the idolatry of a spouse (the hope of a future husband or wife, etc.). Beautiful is the purity that comes from trusting God's absolute authority and absolute goodness, from believing that not just with words but with one's life. I suppose any obedience to Him for this reason is beautiful, but knowing our culture and my own desires, this kind of obedience is almost miraculous.
It is miraculous in that it's only possible by His grace. He knows that without Him, the deck is definitely stacked against purity. That's not a surprise to Him, and it doesn't tempt Him to amend His commandment or take it back. Purity is an outworking of admitting and living in dependence on Him. His grace becomes His grace when it is trusted.
That's a daily, hourly, or (in my case) moment-to-moment decision. The beauty isn't really about the track record, at least not in the way a moralist might think. Purity can come after no mistakes or after thousands, because its author is Christ, not the individual. It's His beauty, His radiance that brings out our own. Likewise, He never withdraws this offer of grace to us. Never.
The voice of authority is the voice of grace. What He says is commanded is commanded; what He says is forgiven is forgiven. We too often seem willing to trust Him with one but not the other. The person who does not trust His voice to command cannot truly trust His voice to forgive, and vice versa.
Most attractive to me is a woman who, regardless of her history, has decided to trust Him in this way. She doesn't destroy her sexuality or wield it as a weapon; she learns to live into it as designed. She knows her strength and her weakness and doesn't spend her life trying to mask either. She doesn't root her identity in her sin (because she knows He forgives) or her self-control (because she knows it's fruit of the Holy Spirit), but in Christ alone. She's not free from struggle, but she's free to struggle. Her purity doesn't come from "being good" but from knowing who she is, who He has declared her to be. He gets the last word in her forgiveness and the last word in her obedience—she has accepted the authority of His voice over her life. She's not trusting God for a husband; she's trusting God to be God, knowing that's more than enough.