1 Corinthians 7:16
For what knowest thou, O wife, whether thou shalt save thy husband? or how knowest thou, O man, whether thou shalt save thy wife? For what knowest thou, O wife, whether thou shalt save thy husband? or how knowest thou, O man, whether thou shalt save thy wife?
A believer already married to an unbeliever is to remain with that spouse and stay faithful in fulfilling marital duties rather than leave. This means not leaving an unbelieving spouse merely because that spouse does not keep the Sabbath. The hope held out is that the believer may help lead the unbelieving spouse to see the truth and win that spouse to God and to salvation. Whether this will happen is not known, so loving and meek faithfulness offers only a possibility.
A wife's influence may accomplish a double work of saving both her husband and herself, preserving herself while saving him. This is done through a sanctified, wise and judicious influence and a consistent life of faith and obedience. It involves elevating the affections and maintaining refined dignity, and it can win a husband back to the truth.
The work calls for wisdom, patience, moral courage and fortitude, with sincere love to God and to the husband as its motive and with strength and grace found in prayer as the right ground for action. Hoping to help the spouse to salvation does not require yielding convictions or setting aside God's claims, for Christ remains the believer's Lord and Master.