I have heard of thee by the hearing of the ear - Referring to the indistinct views which we have of anything by merely hearing of it, compared with the clear apprehension which is furnished by sight. Job had had such views of God as one may obtain by being told of him; he now had such views as are furnished by the sight. The meaning is, that his views of God before were dark and obscure.
But now mine eye seeth thee - We are not to suppose that Job means to say that he actually "saw" God, but that his apprehensions of him were clear and bright "as if" he did. There is no evidence that God appeared to Job in any visible form. He is said, indeed, to have spoken from the whirlwind, but no visible manifestation of Yahweh is mentioned.

I have heard of thee - I have now such a discovery of thee as I have never had before. I have only heard of thee by tradition, or from imperfect information; now the eye of my mind clearly perceives thee, and in seeing thee, I see myself; for the light that discovers thy glory and excellence, discovers my meanness and vileness.

I have (e) heard of thee by the hearing of the ear: but now mine eye seeth thee.
(e) I knew you only before by hearsay, but now you have caused me to feel what you are to me, that I may resign myself over to you.

I have heard of thee by the hearing of the ear,.... From his ancestors, who in a traditionary way had handed down from one to another what they knew of God, his will and worship, his works and ways; and from those who had the care of his education, parents and tutors, who had instilled the principles of religion, and the knowledge of divine things, into him very early; and from such as might instruct in matters of religion in a public manner; and both by ordinary and extraordinary revelation made unto him, as was sometimes granted to men in that age in which Job lived; see Job 4:16. Though he had heard more of God through his speaking to him out of the whirlwind than ever he did before, to which he had attentively listened; and the phrase, hearing by or with the hearing of the ear, denotes close attention; see Ezekiel 44:5;
but now mine eye seeth thee; thy Shechinah, as Jarchi; thy divine glory and Majesty; the Logos, the Word or Son of God, who now appeared in an human form, and spake to Job out of the whirlwind; and whom he saw with the eyes of his body, as several of the patriarchs had seen him, and which is the sense of an ancient writer (n); though no doubt he saw him also with the eyes of his understanding, and had a clearer sight of his living Redeemer, the Messiah, than ever he had before; and saw more of God in Christ, of his nature, perfections, and glory, than ever he had as yet seen; and what he had heard of him came greatly short of what he now saw; particularly he had a more clear and distinct view of the sovereignty, wisdom, goodness, and justice of God in the dealings of his providence with the children of men, and with himself, to which now he humbly submitted.
(n) Euseb. Demonstr. Evangel. l. 1. c. 5. p. 11.

hearing of the ear-- (Psalm 18:44, Margin). Hearing and seeing are often in antithesis (Job 29:11; Psalm 18:8).
seeth--not God's face (Exodus 33:20), but His presence in the veil of a dark cloud (Job 38:1). Job implies also that, besides this literal seeing, he now saw spiritually what he had indistinctly taken on hearsay before God's infinite wisdom. He "now" proves this; he had seen in a literal sense before, at the beginning of God's speech, but he had not seen spiritually till "now" at its close.

Seeth thee - The knowledge which I had of thy nature, perfections and counsels, was hitherto grounded chiefly, upon the instructions of men; but now it is clear and certain, as being immediately inspired into my mind by this thy glorious apparition and revelation, and by the operation of thy holy spirit; which makes these things as evident to me, as if I saw them with my bodily eyes. When the mind is enlightened by the spirit of God, our knowledge of Divine things as far exceeds what we had before, as knowledge by ocular demonstration, exceeds, that by common fame.