Seeing many things. The Prophet himself explains what is the nature of this blindness of which he spoke, and shews that it is double; and this shews clearly that he spoke of the Jews, who by wicked contempt had quenched God's light. Our guilt will be double when we shall come to the judgment-seat of God, if we shut our eyes when he exhibits the light, and shut our ears when he teaches by his word. The heathen nations will indeed be without excuse; but the Jews and others to whom the Lord revealed himself in so many ways, will deserve double condemnation for having refused to see or hear God. We, therefore, who have so many and so illustrious examples set before us at the present day, ought to dread this judgment; for in many persons there will now be found not less blindness or obduracy than formerly existed among the Jews, and not more excusable.

Seeing many things - That is, the people, the Jews, spoken of here as the servants of God. They had had an opportunity of observing many things pertaining to the law, the government, and the dealing of Yahweh. They had often witnessed his interposition in the days of calamity, and he often rescued them from peril. These things they could not but have observed, much as they had chosen to disregard the lessons which they were calculated to convey.
But thou observest not - Thou dost not keep them (תשׁמר tı̂shmor); thou dost not regard them.
Opening the ears - Thou hast thine ears open. They heard the words of the law, and the instructions conveyed by tradition from their fathers, but they did not lay them to heart, or give heed to them (see the note at Isaiah 6:10).

Seeing many things "Thou hast seen indeed" - The text has ראית רבית raith rabith, which the Masoretes in the marginal Keri have corrected to ראות רבות reoth rabboth; as indeed one hundred and seven MSS., and five editions, now have it in the text. This was probably the reading of most of the MSS. of their time; which, though they approved of it, out of some superstition they would not admit into their standard text. But these wretched critics, though they perceived there was some fault, yet did not know where the fault lay, nor consequently how to amend it; and yet it was open enough to a judicious eye: רבות rabboth, sic veteres; et tamen forte legendum, ראות reoth, vide cap. Isaiah 6:9." - Secker. That is, ראית ראות raith, reoth, seeing, thou shalt see. I believe no one will doubt of admitting this as the true reading.
But he heareth not "Yet thou wilt not hear" - For ישמע yishma, read תשמע tishma, in the second person; so all the ancient Versions and forty MSS. of Kennicott's, (four of them ancient), and seventeen of De Rossi's, and perhaps five more. Two others have תשמעו tishmeu, second person plural.

Seeing many things, but thou observest not,.... The Scribes and Pharisees, saw Christ in the flesh; they saw the miracles he did; they saw the blind receive their sight, the lame walk, the lepers cleansed, the deaf hear, and the dead raised; yet they did not give note to these things, and keep them in their minds, and regard them as clear proofs of his being the Messiah:
opening the ears, but he heareth not; they heard John Baptist preach, the forerunner of Christ, and the testimony he bore of him; they heard Christ himself and his apostles; they sometimes opened their ears, and seemed to listen and hear with attention, and wonder at what they heard; and some would own, that never man spake like Jesus; and yet understood not his speech, and hardened their hearts against him; they saw many things with their bodily eyes, but perceived them not with the eyes of their understandings; they heard with their ears, but understood not in their hearts; for their eyes were shut and their ears heavy, Isaiah 6:9.

observest--Thou dost not keep them. The "many things" are the many proofs which all along from the first God had given Israel of His goodness and His power (Deuteronomy 4:32-38; Deuteronomy 29:2-4; Psalm. 78:1-72; Psalm. 105:1-45).
he--transition from the second to the third person. "Opening . . . ears," that is, though he (Israel) hath his ears open (see on Isaiah 6:10). This language, too (see on Isaiah 42:19), applies to Messiah as Jehovah's servant (Isaiah 50:5; Psalm 40:6).

The reproof, which affects Israel a potiori, now proceeds still further, as follows. "Thou hast seen much, and yet keepest not; opening the ears, he yet doth not hear. Jehovah was pleased for His righteousness' sake: He gave a thorah great and glorious. And yet it is a people robbed and plundered; fastened in holes all of them, and they are hidden in prison-houses: they have become booty, without deliverers; a spoil, without any one saying, Give it up again!" In Isaiah 42:20 "thou" and "he" alternate, like "they" and "ye" in Isaiah 1:29, and "I" and "he" in Isaiah 14:30. ראית, which points back to the past, is to be preserved. The reading of the keri is ראות (inf. abs. like שׁתות, Isaiah 22:13, and ערות, Habakkuk 3:13), which makes the two half-verses uniform. Israel has had many and great things to see, but without keeping the admonitions they contained; opening its ears, namely to the earnestness of the preaching, it hears, and yet does not hear, i.e., it only hears outwardly, but without taking it into itself. Isaiah 42:21 shows us to what Isaiah 42:20 chiefly refers. חפץ is followed here by the future instead of by Lamed with an infinitive, just as in Isaiah 53:10 it is followed by the perfect (Ges. 142, 3, b). Jehovah was pleased for His righteousness' sake (which is mentioned here, not as that which recompenses for works of the law, but as that which bestows mercy according to His purpose, His promise, and the plan of salvation) to make thorâh, i.e., the direction, instruction, revelation which He gave to His people, great and glorious. The reference is primarily and chiefly to the Sinaitic law, and the verbs relate not to the solemnity of the promulgation, but to the riches and exalted character of the contents. But what a glaring contrast did the existing condition of Israel present to these manifestations and purposes of mercy on the part of its God! The intervening thought expressed by Hosea (Hosea 8:12), viz., that this condition was the punishment of unfaithfulness, may easily be supplied. The inf. abs. הפח is introduced to give life to the picture, as in Isaiah 22:13. Hahn renders it, "They pant (hiphil of puuach) in the holes all of them," but kullâm (all of them) must be the accusative of the object; so that the true meaning is, "They have fastened (hiphil of pâchach) all of them," etc. (Ges. 131, 4, b). Schegg adopts the rendering, "All his youths fall into traps," which is wrong in two respects; for bachūrı̄m is the plural of chūr (Isaiah 11:8), and it is parallel to the double plural כלאים בּתּי, houses of custodies. The whole nation in all its members is, as it were, put into bonds, and confined in prisons of all kinds (an allegorizing picture of the homelessness and servitude of exile), without any one thinking of demanding it back (השׁב = השׁב, as in Ezekiel 21:32; a pausal form here: vid., Ges. 29, 4 Anm.).

Heareth not - Thou dost not seriously consider the plain word, and the wonderful works of God.