UNEQUALLY YOKED

In Paul's second letter to the church in Corinth, he used a fitting metaphor to get his point across ... they were not to be 'unequally yoked' with nonbelievers. 

Be ye not unequally yoked together with unbelievers: for what fellowship hath righteousness with unrighteousness? and what communion hath light with darkness? 2 Corinthians 6:14

When a team of oxen is mismatched, the stronger of the two has a more powerful draw and the load inevitably veers off course. Instead of working together, the beasts of burden are at odds with one another. 

The apostle's command is often applied to business. When a follower of Christ enters into partnership with an unbeliever, the enterprise will suffer. For the relationship to work at all, one of them has to vacate his moral center and move toward that of the other. More often than not, the believer is pressured into abandoning his Christian principles for the sake of profit and growth. 

The passage is also used to warn against marrying someone outside of the faith. God’s divine plan is for a man and a woman to become 'one flesh' (Genesis 2:24) ... a relationship so intimate that one literally and figuratively becomes part of the other (emblematic of Christ and the church).

A Christian girl once told Charles Spurgeon that she was about to marry a man who was not a believer. He told her of the command ... 'Be ye not unequally yoked'. 

But the young woman argued that she would lift her husband to faith in Christ once they were married. The preacher listened to what she was saying and asked her to stand on a nearby chair. The girl was puzzled ... but obliged him. Once she was in position, he said 'Now try to pull me up to your level'. The girl tugged, but no matter how hard she tried she couldn’t haul him up on the chair with her.

Now it was Spurgeon's turn ... 

'I will try to bring you down to my level and I want you to do your best to remain where you are', he said. Despite the young woman’s best efforts, he easily pulled her down from the chair. 

Then he said to her, 'That is what will happen if you marry that man'.

Understand pilgrim; Paul's admonition is not against interacting with the world ... but against compromising with it. Pressure comes from all sides and you must be vigilant.