We are not our own. We are God’s. God chose us, created us, died for us, called us, and keeps us. He made each human being in His image, and He is conforming every Christian into the image of His Son.
We are not our own. No part of our selves, from tongue to toes, with spouse or with children, among co-workers or community, in the voting booth or at the coffee shop, no part of our lives is ours to do with whatever we want.
We are not our own. John Calvin put it this way in his Institutes of the Christian Religion:
We are God’s: let us therefore live for him and die for him. We are God’s: let his wisdom and will therefore rule all our actions. We are God’s: let all the parts of our life accordingly strive toward him as our only lawful goal. (Calvin, Institutes, 3.7.1)
We are not our own. The apostle Paul put it this way in his first letter to the believers in Corinth:
You are not your own, for you were bought with a price. So glorify God in your body. (1 Corinthians 6:19b-20)
In context, Paul explains that our sexual conduct and physical purity is a type of worship. Our bodies are temples of the Holy Spirit so our conduct is more clear than a neon sign about what type of worship we offer.
Sin dims the light of truth in the worship center. Disobedience rubs dirt into and tears up the carpet of our hearts. But we are not our own. The owner of the building (that is, our bodies) calls us to come to the light, to confess rather than conceal sin, and to be cleansed by faith in Christ. Then the temple is open for business and filled with singing to Him who raises us up by His power.