We can answer this question if we understand the goal of marriage. What is the goal of marriage? It’s to be one with your spouse - to know him or her intimately. This is a reflection of God's relationship with the church (Ephesians 5:31-32).
How can we be intimate with other person? It’s when you share and love the most important thing in your heart. For the Christian, the most important thing in your heart is God. For the non-Christian, it isn’t.
So what inevitably happens is that you have a hard choice to make if you marry a non-Christian. On the one hand, if you want intimacy with your non-Christian spouse, you have to push God out of the center of your heart to make room for her. On the other hand, if you want to keep God in the center, you’ll be forced to put her on the outskirts of your heart and lose intimacy. Either way, it’s a brutal choice at the end of the day, so that’s why I implore you to date and marry a Christian. Make sure you make this conviction BEFORE you think it's time to start dating because it's so easy to compromise if you don't. I've witnessed many Christians who compromise on this one issue, and they aren't walking with Jesus anymore. Practically, you're going to have to say something like the following to your non-Christian friends who want to date you: “Look, every major decision I make involves God and you won't understand that. So every time we make decisions, I have to hide the most important thing in my heart, and that won’t work.”
Other resources:
1. Read this article by Got Questions
2. Listen to the V-DAY Live Ask Us Session Podcast (this very question was asked)
[Answered by Pastor HM]
