1 Corinthians 7:16

It is possible that Paul meant Christians should not separate from their unbelieving spouses because by staying together the unbeliever may eventually become a Christian (cf. 1 Peter 3:1). [Note: Barrett, p. 167.] He may have meant the believer should not oppose the unbeliever’s departing because he may become a Christian through channels other than the witness of the believing spouse. Both possibilities are realistic so even though we cannot tell exactly what the apostle meant here, what we should do is clear. The Christian can have hope that God may bring the unsaved spouse to salvation while the believer does the Lord’s will.

1 Corinthians 7:16 is a positive note on which to close instructions to Christians who have unsaved spouses.