Deuteronomy 4:2 (NLT)
Do not add to or subtract from these commands I am giving you.
We should not stretch or shrink the word of God by adding to or deleting from it. Anyone who does that is interfering with God's sovereign will and is at the risk of condemnation and judgment.
Depending on our biases, we tend to do one or the other. For example, evangelicals tend to include everything in the basket of sexual immorality. The koine Greek word used for immorality is "pornei" which means "forbidden relations." Although evangelicals are generally correct to include adultery, homosexuality, incest, pedophilia, orgies (group sex), lasciviousness and debauchery (sex in public), prostitution, and bestiality in that category, they stretch the truth by including premarital sex in that group. Some preachers even go to the extent of forbidding holding hands or kissing before marriage! That's adding to the word because pre-marital or sex before marriage is not fornication. In fact, the Samaritan woman who was indulging in premarital sex (John 4:16-19) was not condemned by the Lord Jesus. He rebuked her of her lust but stopped short of telling her to stop sinning. Likewise we see an engaged couple celebrating their premarital love in the Song of Songs. At this ministry I neither bless nor condemn premarital sex. The Lord does not bless couples living together before marriage. That blessing is only upon a covenant marriage. However, God does not condemn such heterosexual couples either.
The other extreme is apparent in liberal, orthodox, Catholic and fundamentalist denominations. Although such churches have an official doctrine against immorality they seldom preach or practice it. In fact a majority of them openly support "gay marriages" and vote for them, which is an abomination. This is an example of deleting from scripture.
As servants of God we have to rightly divide the word of God without adding or subtracting from it (2 Timothy 2:15).