lished in Palestine. Many Jews have migrated there. But there has been no fulfillment of Isaiah 6:11-12. If the land was previously desolate, and without inhabitant, and is now inhabited by God’s people, wouldn’t Isaiah’s prophecy imply that the time when the meaning of his prophecies would be known had come?
Evidently, Isaiah must have referred to another land. The prophecy could refer to the land of promise in its spiritual sense. It can’t be the literal land, in the sense Alexander supposed above. The Jewish people now living in the modern Jewish state are no more enlightened about the Gospel, than the Jews of Rome were when Paul was there, and when the last verses of the book of Acts were written.
Alexander interpreted the land in a spiritual sense, in his comments on Isaiah 57:13, where he explained “he that putteth his trust in me shall possess the land” as having “a wider explanation, in which the possession of the land is an appointed symbol of the highest blessings which are in reserve for true believers here and hereafter.”  This is the spiritual meaning of the land; the land of Canaan was a type and shadow of the spiritual blessing promised to believers.
Ebenezer Henderson (1784-1858) understood the healing mentioned in Isaiah 6:10 as referring to spiritual conversion, and the forgiveness of sins. He wrote, “The healing referred to is the entire moral recovery which sinners experience on their conversion to God; and, as pardon is essential to such recovery, healing and forgiveness of sins came to be regarded by the Hebrews as synonymous.”  Henderson commented on the Hebrew terms used in verse 11: 
11. עַ֣ד אֲשֶׁר֩ אִם This accumulation is designed to give intensity to the statement, and thereby to intimate, in such connexion, the great length of time during which the obstinacy of the Jews should be evinced. Comp. Gen. xxviii. 15; Numb, xxxii. 17. תִּשָּׁאֶ֥ה שְׁמָמָֽה lit. be laid waste, a desolation, for “be utterly wasted.”
Like many scholars, Otto Kaiser thought that the prophecy of Isaiah 6:9-11 referred to the Babylonian captivity, but the references in the New Testament show that the enlightenment that was promised when the land was utterly desolate had not come. He wrote: 
As the answer shows, the prophet’s question, ‘How long, O Lord?’ in v. 11a, which has its parallel in the lament, relates not so much to the duration of his activity, which is to advance the hardening of people’s hearts, as to the duration of that hardening. Here it is again clear that the narrator is looking beyond the lifetime of Isaiah to the catastrophe of 587. Because the so-called memorial introduced by ch. 6 ends in a word of hope (cf. 8:17), God’s answer envisages the end of the hardening and the possibility given with it of a new beginning to his history.
Johann Peter Lange thought that Isaiah’s prophecy meant there would be a complete desolation of the land. He wrote: 
5. Then said I —
Vers. 11-13. The announcement of the judgment of hardening in vers. 9, 10 sounds quite absolute. Yet the Prophet hears underneath all that it is not so intended. It is impossible that the Lord should quite and forever reject His people, and abrogate the promises given to the fathers. He asks, therefore, “How long, Lord?” (соmр. Ps. vi. 4; xc. 13; Hab. ii. 6). He would say: What are to be quantitively and qualitatively the limits of that judgment of hardening? The answer is: First there must be an entire desolation and depopulating of the land; and when at last still a tenth of the inhabitants is in the land, that tenth part also must be decimated till nothing is left but the stump of a root or stem. That shall then be the seed of a holy future. The meaning of the words is perfectly clear.
The construction is as follows: and still there is in it (the land) a tenth part, and this is again decimated—after the manner of or in resemblance to the terebinth and oak, in which, when felled, a stump remains, its stump (of the tenth) is holy seed. Therefore a stump always remains, and that suffices to guarantee a new life and a new glorious future. This 