Jamieson, Fausset and Brown on 1 Corinthians 14:22

22. Thus from Isaiah it appears, reasons Paul, that "tongues" (unknown and uninterpreted) are not a sign mainly intended for believers (though at the conversion of Cornelius and the Gentiles with him, tongues were vouchsafed to him and them to confirm their faith), but mainly to be a condemnation to those, the majority, who, like Israel in Isaiah's day, reject the sign and the accompanying message. Compare "yet ... will they not hear Me" (1Co 14:21). "Sign" is often used for a condemnatory sign (Eze 4:3, 4; Mt 12:39-42). Since they will not understand, they shall not understand.

prophesying ... not for them that believe not, but ... believe--that is, prophesying has no effect on them that are radically and obstinately like Israel (Is 28:11, 12), unbelievers, but on them that are either in receptivity or in fact believers; it makes believers of those not wilfully unbelievers (1Co 14:24, 25; Ro 10:17), and spiritually nourishes those that already believe.