2 Corinthians - Be ye not unequally yoked together with unbelievers: for what fellowship hath righteousness with unrighteousness? 1 Corinthians - Be not deceived: evil communications corrupt good manners.2 Corinthians -18 - Be ye not unequally yoked together with unbelievers: for what fellowship hath righteousness with unrighteousness? Proverbs - Favour [is] deceitful, and beauty [is] vain: [but] a woman [that] feareth the LORD, she shall be praised.2 Timothy 3:1-5 - This know also, that in the last days perilous times shall come.
The principle stated in 2 Corinthians -18 would seem to apply to marriage as well, and some might see it as applying to dating.
I suspect that this would be an inferential conclusion, and thus would have to be considered a matter of personal conviction, rather than as a clear biblical prohibition.
One could certainly ask, “If a Christian cannot marry an unbeliever, why would they ever date one? I think one can have a friendship relationship with an unbeliever of the opposite sex, without entering into a dating relationship.
For what do righteousness and wickedness have in common? What harmony is there between Christ and Belial [Satan]?
What does a believer have in common with an unbeliever?