Paul has been talking about how people build on the church. Now he reminds them what kind of building it is. "Know ye not" appeals to something they should already know. Barnes explains that Paul turns his building picture onto the Corinthians themselves: "they were the sacred temple which God had reared." And a temple is defined by who lives there. Barnes says of God's Spirit, "His residence is with them; and He is in their midst." Paul's aim is to make a divided, careless church see how holy it really is.

Paul draws the consequence at once: "If any man defile the temple of God, him shall God destroy; for the temple of God is holy, which temple ye are" (1 Corinthians 3:17). Then he warns, "Let no man deceive himself" (1 Corinthians 3:18). He ends the chapter by reminding them whose they are: "ye are Christ's; and Christ is God's" (1 Corinthians 3:23).

The "ye" in this verse is plural: Paul is speaking to the church as a whole. Later in the letter he applies the same picture to each believer's body: "your body is the temple of the Holy Ghost which is in you" (1 Corinthians 6:19). Matthew Henry says the verse may be understood of the church as a whole or of every single believer. The Greek word for temple here is naos, and "dwelleth" is oikei, "dwells," from the word for house. Gill compares the church to the temple of Solomon, and in his note on the next verse he cites a rule from the Mishna (the early collection of Jewish oral law) that a man might not go into that temple with his staff, his shoes, or his purse, or make it a thoroughfare. The sacred place was to be treated with reverence.

God has always wanted to live among His people. Barnes notes that as God once dwelt among the Jews in the temple, "so he dwells among Christians." Paul quotes this promise later: "I will dwell in them, and walk in them; and I will be their God, and they shall be my people" (2 Corinthians 6:16). The church is not a building people visit. It is the people God lives in.

Gill draws another truth from the verse. Only God can have a temple, so the Spirit's dwelling in believers "furnishes out a considerable proof of the deity and distinct personality of the Spirit." That is why Paul's warning is so serious (1 Corinthians 3:17). To tear apart the church by pride and division is to damage the place where God lives.