1 Corinthians 14:21 - Matthew Poole's English Annotations on the Holy Bible

In the law it is written: by the law here is meant the Old Testament, (as in many other texts, 1 Thessalonians 10:34, 1 Thessalonians 15:25), so called (as some think) in opposition to the words of the scribes. The words following are quoted out of Isaiah 28:11,12: For with stammering lips and another tongue will he speak to this people. To whom he said: This is the rest wherewith ye may cause the weary to rest; and this is the refreshing: yet they would not hear. But there is nothing more ordinary, than for the penmen of the Scriptures of the New Testament to quote passages out of the Old, keeping not so much to the words as to the sense; nor quoting them all, but so many of them as serve for their purposes. The words in the prophet are a threatening, that because God had brought the Jews into Canaan, and promised them rest there, upon their obedience to his commandments, and they would not hear, he would now take another course with them, speaking to them with men of stammering lips, and of another language; meaning the Chaldeans and Babylonians, with whom in captivity they conversed afterwards for seventy years. The sense is much the same (as some think); for they that speak to others in and with strange tongues, are like those that stammer at others, which looks more like a mocking them than an instructing them. Others make the gift of tongues, under the New Testament, to be within the prophecy of Isaiah; as if the prophet's words contained both a threatening, to speak to the Israelites with the strange tongues of the Chaldeans; and a promise under the gospel, to speak to them with the tongues of the apostles and others, tuned to various tunes, as men of several nations could understand. Others make this the sense, as if the prophet complained, that the people were so mad, that they regarded no more God speaking to them, than they would have regarded one chattering with a strange tongue. And they think, the apostle checks them for being so ambitious of speaking with strange tongues, whenas their being so spoken to was by the prophet threatened as a judgment upon them. And yet they will not hear me, nor hearken to and obey me.