What does Ephesians 5:31 mean?

This verse is a paraphrase of Genesis 2:24. Paul reminds readers that marriage turns two people into "one flesh" or one body or unit. God's original design for marriage was one man and one woman in lifelong relationship. When asked about divorce, Jesus referred to this same passage to support that marriage is intended as a lifelong relationship (Matthew 19:5–6; Mark 10:8), though the New Testament elsewhere provides some legitimate reasons for divorce. Paul also quotes Genesis 2:24 in 1 Corinthians 6:16, emphasizing purity in Christian sexuality.

Another reason for this verse's importance is that Paul added a prior biblical principle to support his argument. Though Paul's letter is inspired revelation, it is further strengthened by its use and consistency with prior revelation. Marriage has been defined for God's people since the earliest times and was not changed in the early church. Instead, Paul restated this teaching and gave an even higher standard by comparing the marriage relationship with Christ and the church.