For with stammering lips and another tongue will he speak to this people.
Read Chapter 28
Augustine of Hippo
Thus at times all the sayings of the ancient covenant of the sacred Scriptures are designated together by the name of law. For the apostle cites the testimony from the prophet Isaiah, where he says, “In other tongues and with other lips I will speak to this people,” and yet he had prefaced this by saying, “In the law it is written.” - "On the Trinity 15.17.30"
They spoke with strange tongues and not those of their native land; and the wonder was great, a language spoken by those who had not learned it. And the sign is to them that do not believe, not to them that believe, that it may be an accusation of the unbelievers, as it is written, “With other tongues and other lips will I speak to this people, and not even so will they listen to me, says the Lord.” But they heard. Here stop a little and raise a question. How are you to divide the words? For the expression has an ambiguity, which is to be determined by the punctuation. Did they each hear in their own dialect so that if I may so say, one sound was uttered but many were heard; the air being thus beaten and, so to speak, sounds being produced more clear than the original sound? Or are we to put the stop after “they heard” and then to add “them speaking in their own languages” to what follows, so that it would be speaking in the hearers’ own languages, which would be foreign to the speaker...
Someone might well ask how the apostles drew to themselves all these people. How did men who spoke only the language of the Jews win over the Scythian, the Indian, the Sarmatian and the Thracian? Because they received the gift of tongues through the Holy Spirit. Not only did the apostles say this but also the prophets when they made both these facts clear, namely, that the apostles received the gift of tongues and that they failed to win over the Jews. Hear how the prophet showed this when he said, “ ‘In foreign tongues and with other lips I shall speak to this people, and in this way they shall not hear me,’ says the Lord.” - "Demonstration Against the Pagans 7.2"
It is not therefore necessary that every one of the faithful should cast out demons or raise the dead or speak with tongues, but such a one only who is graciously given this gift. For [it may contribute] to the salvation of the unbelievers, who are often put to shame not with the demonstration of the world but by the power of the signs, that is, such as are worthy of salvation. For all the ungodly are not affected by wonders, and hereof God is a witness, as when he says in the law: “With other tongues will I speak to this people, and with other lips, and yet will they by no means believe.” For neither did the Egyptians believe in God, when Moses had done so many signs and wonders; nor did the multitude of the Jews believe in Christ, as they believed Moses, who yet had healed every sickness and every disease among them. - "Constitutions of the Holy Apostles 8"