What? know ye not...? — These verses read better rendered thus: Do you not know that your body is the temple of the Holy Ghost which is in you? Which you have from God, and you are not your own. For you were bought with a price. Glorify God then in your body.
There are two reasons why we are not our own. (1) The Spirit which has possession of our bodies is not our own, but given us “of God.” (2) We have been bought with a price, even the blood of Christ; it is a completed purchase (1 Peter 1:18-19). Our bodies not being our own to do as we like with, we have no right to give them over unto sin. The last words of the verse are not a cold logical deduction from the previous argument, but rather an earnest exhortation suggested by the solemn thought of our oneness with Christ, and the price paid by Him to make us His.
The words “and in your spirits,” which are in the Authorised version, are not in the older Greek MSS. They were probably added to give a kind of verbal completeness to the exhortation. They only tend, however, to weaken the force of the passage as St. Paul wrote it. The dignity of the body is the subject of the previous passage, and the necessity for its purity the sole theme of the entire argument.