16 Otherwise, if you bless with the spirit, how can any one in the position of an outsider say the "Amen" to your thanksgiving when he does not know what you are saying? 17 For you may give thanks well enough, but the other man is not edified. 18 I thank God that I speak in tongues more than you all; 19 nevertheless, in church I would rather speak five words with my mind, in order to instruct others, than ten thousand words in a tongue. 20 Brethren, do not be children in your thinking; be babes in evil, but in thinking be mature.
21 In the law it is written, "By men of strange tongues and by the lips of foreigners will I speak to this people, and even then they will not listen to me, says the Lord." 22 Thus, tongues are a sign not for believers but for unbelievers, while prophecy is not for unbelievers but for believers. 23 If, therefore, the whole church assembles and all speak in tongues, and outsiders or unbelievers enter, will they not say that you are mad? 24 But if all prophesy, and an unbeliever or outsider enters, he is convicted by all, he is called to account by all, 25 the secrets of his heart are disclosed; and so, falling on his face, he will worship God and declare that God is really among you.
Matthew Henry's Commentary on 1 Corinthians 14:16-25
Commentary on 1 Corinthians 14:15-25
(Read 1 Corinthians 14:15-25)
There can be no assent to prayers that are not understood. A truly Christian minister will seek much more to do spiritual good to men's souls, than to get the greatest applause to himself. This is proving himself the servant of Christ. Children are apt to be struck with novelty; but do not act like them. Christians should be like children, void of guile and malice; yet they should not be unskilful as to the word of righteousness, but only as to the arts of mischief. It is a proof that a people are forsaken of God, when he gives them up to the rule of those who teach them to worship in another language. They can never be benefitted by such teaching. Yet thus the preachers did who delivered their instructions in an unknown tongue. Would it not make Christianity ridiculous to a heathen, to hear the ministers pray or preach in a language which neither he nor the assembly understood? But if those who minister, plainly interpret Scripture, or preach the great truths and rules of the gospel, a heathen or unlearned person might become a convert to Christianity. His conscience might be touched, the secrets of his heart might be revealed to him, and so he might be brought to confess his guilt, and to own that God was present in the assembly. Scripture truth, plainly and duly taught, has a wonderful power to awaken the conscience and touch the heart.