13 Let no one say in his heart, “God cares not for sins of the flesh.” “Do you not know,” says the Apostle, “that you are the temple of God, and the Spirit of God dwells in you? If any man defile the temple of God, him will God destroy.” “Let no man deceive himself.” But perhaps a man will say, “My soul is the temple of God, not my body,” and will add this testimony also, “All flesh is as grass, and all the glory of man as the flower of grass.” Unhappy interpretation! conceit meet for punishment!
The flesh is called grass, because it dies; but take heed that that which dies for a time, rise not again with guilt. Would you ascertain a plain judgment on this point also? “Do you not know,” says the same Apostle, “that your body is the temple of the Holy Ghost which is in you, which you have of God?” Do not then any longer disregard sins of the body; seeing that your “bodies are the temples of the Holy Ghost which is in you, which you have of God.” If you disregarded a sin of the body, will you disregard a sin which you commit against a temple?
Your very body is a temple of the Spirit of God within you. Now take heed what you do with the temple of God. If you were to choose to commit adultery in the Church within these walls, what wickedness could be greater? But now you are yourself the temple of God. In your going out, in your coming in, as you abide in your house, as you rise up, in all you are a temple. Take heed then what you do, take heed that you offend not the Indweller of the temple, lest He forsake you, and you fall into ruins.
“Do you not know,” he says, “that your bodies” (and this the Apostle spoke touching fornication, that they might not think lightly of sins of the body) “are the temples of the Holy Ghost which is in you, which you have of God, and you are not your own?” For “you have been bought with a great price.” If you think so lightly of your own body, have some consideration for your price.
Source: Sermons on Selected Lessons of the New Testament (New Advent)