Unbelief, Fornication, and the Call to Prophecy

Written on 16 May 2025.

Unbelief, Fornication, and the Call to Prophecy

In the King James Bible, all sin is condemned, but not all sin is equal in consequence. While some sins may seem more serious from a human perspective, Scripture gives particular weight to the sin of unbelief. This article explores the biblical view of unbelief as the greatest sin, God's forgiveness of all other sins for the believer, and the post-salvation invitation to seek spiritual gifts such as prophecy.

Unbelief: The Greatest Sin

Unbelief is repeatedly shown in the Bible to be the root sin that separates a soul from eternal life. It is unbelief that keeps a person condemned:

He that believeth on him is not condemned: but he that believeth not is condemned already... (John 3:18)

He that believeth on the Son hath everlasting life: and he that believeth not the Son shall not see life; but the wrath of God abideth on him. (John 3:36)

The gospel declares that salvation comes by grace through faith:

For by grace are ye saved through faith; and that not of yourselves: it is the gift of God. (Ephesians 2:8)

Thus, unbelief is the greatest sin because it rejects God's gift of eternal life. Without faith, no other sin can be forgiven.

Fornication: A Serious but Forgivable Sin

Fornication is described as a grievous sin in Scripture. It is singled out as a sin against the body:

Flee fornication. Every sin that a man doeth is without the body; but he that committeth fornication sinneth against his own body. (1 Corinthians 6:18)

However, fornication is not called the greatest sin, nor is it unforgivable. In fact, those who have committed such sins are shown in Scripture to be washed and justified:

And such were some of you: but ye are washed, but ye are sanctified, but ye are justified in the name of the Lord Jesus, and by the Spirit of our God. (1 Corinthians 6:11)

The moment a person believes on the Lord Jesus Christ, they are eternally saved, and all sins — including fornication — are forgiven:

To him that worketh not, but believeth on him that justifieth the ungodly, his faith is counted for righteousness. (Romans 4:5)

Be it known unto you therefore, men and brethren, that through this man is preached unto you the forgiveness of sins: And by him all that believe are justified from all things... (Acts 13:38–39)

Thus, fornication is serious, but it is not unforgivable to those who believe.

After Salvation: Seek That Ye May Prophesy

Once saved, the believer is called to grow in faith and may seek spiritual gifts. Among these, prophecy is especially encouraged:

Follow after charity, and desire spiritual gifts, but rather that ye may prophesy. (1 Corinthians 14:1)

Ye may all prophesy one by one, that all may learn, and all may be comforted. (1 Corinthians 14:31)

Paul affirms that prophecy edifies the church, speaking unto men for exhortation and comfort (1 Corinthians 14:3). Not everyone is a prophet, but all are encouraged to desire the gift and be used by the Spirit as God wills.

Importantly, any claim to prophecy must align with Scripture:

If any man think himself to be a prophet, or spiritual, let him acknowledge that the things that I write unto you are the commandments of the Lord. (1 Corinthians 14:37)

No prophet has the authority to contradict the gospel or doctrine given through the apostles. The test of a true prophet is fidelity to the written Word.

Conclusion

The greatest sin in the Bible is not fornication but unbelief, which prevents the forgiveness of all other sins. Once a person is saved by believing the gospel, they are forgiven entirely — including of sexual sins — and are free to seek the deeper gifts of the Spirit. Among these, prophecy is especially to be desired, as it builds up the church and speaks comfort to men. As always, the true measure of a prophet is found in his agreement with the commandments of the Lord as preserved in the Scriptures.