We see in 1 Corinthians 14:22 that tongues are a sign for unbelievers and prophesy is a sign for believers, yet in the latter verses it appears to indicate the opposite, that tongues are sign for believers and prophesy a sign for unbelievers. What did Paul mean when he said this?
I included verse 21 because it seems to indicate that the speaking in foreign tongues like what we see happen at Pentecost is descriptive of how tongues are a sign to unbelievers, naturally a foreigner speaking your tongue will serve as a sign from God. I've heard the interpretation that tongues means two different things in this passage but I don't see that as justifiable since it talking about tongues in such a close proximity without any distinction.
1 Corinthians 14:21-25
21 In the Law it is written, “By people 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 a sign not for unbelievers but for believers. 23 If, therefore, the whole church comes together and all speak in tongues, and outsiders or unbelievers enter, will they not say that you are out of your minds? 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.