What does John 5:23 mean?

Jesus makes an extremely important point here. This relates not only to salvation, but also to the idea of who Christ is and how He relates to God. In prior verses, Jesus pointed out how He is equal to God in various ways. These include having the same works (John 5:19), love (John 5:20), and judgment (John 5:22). Jesus has also claimed authority over life and death (John 5:21).

Now Jesus ties these other points together. God expects the Son—Jesus—to be given honor, just as God is to be given honor. This makes sense, given all the other divine qualities Jesus possesses. If Jesus really does have the power, love, judgment, and authority of God, He deserves the same honor and respect as God—because that would mean He is God.

This is also for our understanding of salvation. If Jesus is God, and is owed the same honor as God, then a person cannot reject the Son—Jesus Christ—and claim to be right with the Father. This matches other claims where Jesus plainly states that He is the one and only way to be reconciled with God (John 3:16, 36; 14:6). Calling Jesus only one of many ways to God is to dishonor Him, by calling Him a liar. Downgrading Him to something less than divine, or to merely a "good teacher" also dishonors Him. In short, those who reject the divinity of Christ are rejecting God Himself.

The next verse emphasizes this claim with the familiar phrase, "truly, truly," or "verily, verily."