Wherefore - Thus, (Ὥστε Hōste), or wherefore. The apostle does not mean to say that what he was about to state was a direct conclusion from the passage of Scripture which he had quoted, but that it followed from all that he had said, and from the whole view of the subject. “The true statement or doctrine is, that tongues are for a sign,” etc.
Tongues - The power of speaking foreign languages.
Are for a sign - An “indication,” an evidence, or a proof that God has imparted this power, and that he attends the preaching of the gospel with his approbation. It is a “sign,” or a “miracle,” which, like all other miracles, may be designed to convince the unbelieving world that the religion is from God.
Not to them that believe - Not to Christians. They are already convinced of the truth of religion, and they would not be benefited by that which was spoken in a language which they could not understand,
But to them that believe not - It is a miracle designed to convince them of the truth of the Christian religion. God alone could confer the power of thus speaking; and as it was conferred expressly to aid in the propagation of the gospel, it proved that it was from God; see the note on Acts 2:1-15.
But prophesying - Speaking in a calm, connected, didactic manner, in language intelligible to all under the influence of inspiration; see notes on 1 Corinthians 14:1.
For them that believe not - Is not particularly intended for them; but is intended mainly for the edifying of the church. It is not so striking, so replete with proofs of the divine presence and power as the gift of tongues. Though it may be really under the influence of the Holy Spirit, and may be really by inspiration, yet it is not so evidently such as is the power of speaking foreign languages. It was, therefore, better adapted to edify the church than to convince gainsayers. At the same time the “truths” conveyed by it, and the consolations administered by it, might be as clear evidence to the church of the attending power, and presence, and goodness of God, as the power of speaking foreign languages might be to infidels.