This verse is a quotation from Isaiah 6.10, though its form in John differs from both the Hebrew and the Septuagint. Probably John was quoting freely, perhaps from memory, and adapting the material to suit his purpose. In place of God (literally “he”) has blinded their eyes, and closed their minds (literally “hardened their heart”) the Hebrew text reads “make (imperative) the heart of this people fat, and their ears heavy, and shut their eyes….” It should be noted that John omits “ears” and speaks of the “eyes” before the “heart.” (In Hebrew “heart” functions as the equivalent of “mind” for the western reader.) Also, John omits the phrase “of this people.” However, the most noticeable difference is that John changes the imperatives of the Hebrew text (“make … shut”) to a statement has blinded, with God as the assumed subject, as Good News Translation makes explicit. Quite likely John makes the changes to emphasize that the judgment on the Jews is in reality the action of God. This conclusion is supported by the observation that John’s last line follows the Septuagint (literally “and I will heal them”) instead of the “divine passive” of the Hebrew text (“and be healed”).
It may be difficult to preserve the type of double parallelism of this verse. Note, for example, that the first line refers to the eyes and the second line to the mind, while the third line refers back to the eyes and the fourth line to the mind. It may be necessary to bring together the lines referring to the eyes and those referring to the mind, for example, “God has blinded their eyes so that they cannot see, and he has closed their minds so that they cannot understand.” If it is difficult to speak of “closing minds” an equivalent may be “make their minds slow” or “make their minds hard.” Or an equivalent may be “he made them stupid,” in the sense that “they could not think correctly.” If verse 39b is translated “God spoke further through the prophet Isaiah and said,” then in verse 40, instead of the third person (God has blinded … and closed), the first person, referring to God, may be used throughout: “I have blinded their eyes, and I have closed their minds.”
They would not turn to me, says God, for me to heal them is literally “lest they … turn, and I will heal them.” It is clearly implied by the context that the turning is to God, and Good News Translation makes this explicit by including to me, says God. It may be made explicit in another way. That is, if verse 39 is made to read “God spoke through the prophet Isaiah, and also said,” then in verse 40 a first person reference can be made to God throughout (“I have blinded their eyes…. And they would not return to me, for me to heal them”).
It is important to note that the clause and they would not turn to me is still a part of the expression of purpose stated in the beginning of the third line. However, since the second part of verse 40 is to be understood as a quotation, it may be necessary to break the sentence after the fourth line and introduce the direct quotation as “God says, I did this so that they would not turn to me in order for me to heal them.”
It is difficult to overestimate the significance of Isaiah 6.10 for the New Testament. It is used in the Synoptic Gospels (see Matt 13.13-15; Mark 4.12; Luke 8.10) to explain why the people did not understand Jesus’ teaching in parables concerning the kingdom. Paul quotes it in Acts 28.26-27 to explain why the Jews did not accept the gospel which he proclaimed to them. And here John uses it to explain why the Jews rejected Jesus.
Quoted with permission from Newman, Barclay M. and Nida, Eugene A. A Handbook on the Gospel of John. (UBS Handbook Series). New York: UBS, 1980. For this and other handbooks for translators see here .