Reasons not to marry an unbeliever
Here is a good article from the Gospel Coalition on Reasons not to Marry an Unbeliever.
(If you’ve been reading here a while you’d have read my little story of my unexpected encounter with this “problem”, but if not, it’s under the label of non-Christian boys down the side and the 'nonny enticement' posts. In short, I went along to an ordination service for friends – last place on earth you expect you are going to meet unbelievers – and the fellow I called Ignis fatuus (because my life is full of Jane Eyre references), being the sort of fellow he is, was there also in support of the same friend. Following that he came along to church a couple of times, asked me out during one of those visits, so we had a coffee, during which I did end up needing to explain to him why I couldn’t go out with him. Then independently he went and spoke to our mutual newly-ordained friend and decided he was going to come along and do the Simply Christianity course at my church, so he did, and for those six weeks he was around, and I was just waiting to see what the outcome might be. Sadly, he decided it wasn’t for him, and so that was where it ended. (And the truth is, even if he had given his life to Christ there and then, it still would not have been an easy or particularly ideal situation.) There was no real harm done, and I am very thankful for that, but there were times I found it difficult (and I found out what can go through a person's head in that scenario!) and it caused me to have my own little wrestle with this issue.)