Answer:
You have a good question.
First, the Bible clearly says that we should not be yoked with unbelievers:
2 Corinthians 6:14,15 NIV
Do not be yoked together with unbelievers. For what do righteousness and wickedness have in common? Or what fellowship can light have with darkness? What harmony is there between Christ and Belial? What does a believer have in common with an unbeliever?
In another version, The Message, these verses are worded this way, which make it a bit easier to understand how it applies to our lives: 2 Corinthians 6:14,15 – The Message
Don’t become partners with those who reject God. How can you make a partnership out of right and wrong? That’s not partnership; that’s war. Is light best friends with dark? Does Christ go strolling with the Devil? Do trust and mistrust hold hands?
A dating relationship should keep Christ at the center of the relationship and bring glory to God. I like to think of it this way: does this relationship bring me closer to God or does it separate me further from Him? A dating relationship between two believers is Christ-centered, while one that is between a believer and non-believer cannot be Christ-centered.
It is clear that like Jesus, we are to go into all the world and preach the Good News and make disciples. This means we are to be with non-believers. But dating is a different situation, and “missionary dating” is a risky situation that can not only carry you further from the Lord, but also the person you are dating. A relationship based on Christ must be with another believer.
Every dating relationship may bring a potential mate. Out of Adam, God brought a perfect mate for him. In every relationship stay close to God and put Jesus as the center, not worldly love. Living in God’s will allows Him to bring us the mate that is equally yoked to us and is perfect for us.