Translation
In the Law it is written:
Go to footnote numberBy other tongues and by other lips I will speak to this people, and not [even] in this manner will they hear me into [themselves].
Go to footnote numberParaphrase
In the Hebrew Scriptures it is written “Through unknown languages and through strange-sounding speech I will communicate my desires to the people of Israel, and yet not even then will they listen intently to what I say and take it to heart and comply with it.
Footnotes
1
Here “the Law” really means the entirety of the Hebrew Scriptures because the source is Isaiah 28:9-12. It is not a direct quote, but rather a very free rendition of the Septuagint’s translation of that passage into Greek.
2
The compound word “hear into” was used for emphasis and had the force of “to grasp what is said and extend it to its purpose of result”. It can be rendered “hear deeply, listen intently, give ear to, assent to, comply with.”
“BY OTHER TONGUES I WILL SPEAK TO THIS PEOPLE”
This statement was taken from Isaiah 28:9-12 and adapted by Paul. The point of it is this: God used the strange-sounding language of the Assyrians and then the Babylonians to discipline the Israelites from the northern tribes and then the southern tribes respectively.
The Assyrians were known as “dividers.” God used them to say, “You like division, therefore I will send you to the ones who specialize in division. The Assyrians will teach you the full consequences division.” Of those who were taken in captivity to Assyrian, basically none of them returned to Israel.
The Jews saw the Babylonians as ones living in “Confusion.” God used this to say, “You like confusion, therefore I will allow the masters of confusion to teach you the full consequences of confusion.” Of those that were taken as captives to Babylon, only a small percentage returned to Israel.
According to Is 28:9-14, this disciplinary act was necessary because they had refused to listen to the tongues of the prophets whom they could understand. The Isaiah 28 passage is about punishment, but later, in v. 16, there is a hint that points to Jesus.
In Acts chapter 2 the statement came true again, although not as an act of discipline, but to get the attention of Jews who did not yet believe in Jesus as savior and Messiah.