The church building is the house of God, which is why you have to be reverent and quiet inside it

The Greek word naos refers specifically to the inner sanctuary of a temple: the actual dwelling place of a deity, as distinct from hieron, the wider temple complex and courts. Paul uses naos three times to describe people, not buildings. To the church at Corinth he writes that 'you are a sanctuary of God and the Spirit of God dwells in you'; naos is the word translated 'sanctuary' there (1 Corinthians 3:16, and he says the same of the individual body in 1 Corinthians 6:19). In Ephesians 2:19-22, believers are 'no longer strangers… but… of God's household,' and 'the whole building, being joined together, is growing into a holy sanctuary in the Lord'; naos again, present tense, still under construction, made of people being joined to each other. Peter uses a related image without the word naos itself: believers are 'living stones… built up as a spiritual house for a holy priesthood' (1 Peter 2:5). Three different New Testament writers, three passages, all landing on the same move: temple language gets pulled off the architecture and put onto the gathered and individual believer.

That's a real theological point, and it's worth being fair to the instinct it's correcting rather than steamrolling it. Sacred space is a genuine biblical category: Eden, the tabernacle, Solomon's temple, and the final vision of a city with no temple at all because 'the Lord God the Almighty and the Lamb are its sanctuary' (Revelation 21:22) all treat the presence of God as something that sanctifies a place. The New Testament isn't saying that category was a mistake. It's saying the category moved: God's dwelling now sits in his people rather than in a building, so the reverence instinct people have walking into a church isn't wrong, it's just aimed at the wrong address. A church building can still be useful, dedicated, and set apart for gathering; that's a real thing a congregation can choose to do with a space. It's just not what the Bible calls 'the house of God' in the way the phrase usually gets used.