Open thou mine eyes - Margin, "Reveal." So the Septuagint and the Latin Vulgate. The Hebrew word means to be naked; then to make naked, to uncover, to disclose, to reveal. Here it is the same as "uncover;" that is, take away from the eyes what is before them to prevent clear vision. Compare Numbers 22:31; Numbers 24:4, Numbers 24:16.
That I may behold wondrous things - Things which are suited to excite wonder and amazement: that is, things which are secret or hidden from the common view; the deep, spiritual meaning of the word of God. By natural vision he might see the surface - the letter; to see the deep, hidden, real, meaning, he needed the special influence of God. Compare 1-Corinthians 2:12, 1-Corinthians 2:14-15. He believed that there were such things in the law of God; he desired to see them.
Out of thy law - Out of the written word; out of the Scriptures. The word "law" here is used to denote "all" that God had revealed to mankind; all that is contained in the volume of inspiration. The truths taught here are
(1) That there are deep, hidden, secret things in the word of God, which are not perceived by the natural man;
(2) That those things, when understood, are suited to excite wonder, or to fill the mind with admiring views of God;
(3) That a special illumination of God is necessary that man may perceive these things; and
(4) That the proper understanding of these things is connected with prayer, and can be hoped for only in answer to prayer.
No one has a proper appreciation of divine truth - of the beauty, the spiritual meaning, the grandeur, the sublimity of the Bible - until he is a renewed - a praying - man. Compare the notes at 1-Corinthians 2:6-15.

Open thou mine eyes - גל עיני gal eynai, reveal my eyes, illuminate my understanding, take away the veil that is on my heart, and then shall I see wonders in thy law. The Holy Scriptures are plain enough; but the heart of man is darkened by sin. The Bible does not so much need a comment, as the soul does the light of the Holy Spirit. Were it not for the darkness of the human intellect, the things relative to salvation would be easily apprehended.

Open thou mine eyes,.... The eyes of my heart or understanding, as Kimchi; or, "reveal mine eyes" (t); take off the veil from them: there is a veil of darkness and ignorance on the hearts of all men, with respect to divine and spiritual things; their understandings are darkened, yea, darkness itself. This veil must be removed; the scales must drop from their eyes; their eyes must be opened and enlightened, before they can discern spiritual things contained in the word of God; and even good men need to have the eyes of their understandings more and more enlightened into these things, as the psalmist here petitions, and the apostle prays for his Ephesians, Ephesians 1:17;
that I may behold wondrous things out of thy law; the law strictly taken, which had great and excellent things in it; and was wonderful for the compendiousness of it; for the justice, holiness, and equity of its precepts; especially for its spirituality, and above all for Christ, being the end of it; the two last more particularly could only be discerned by a spiritual man: or rather the five books of Moses, the almost only Scriptures extant in David's time, in which there were many wonderful things concerning Christ; some delivered by way of promise and prophecy of him, under the characters of the seed of the woman, the seed of Abraham, the Shiloh, and the great Prophet; and many others in dark figures, types, and shadows, which required a spiritual sight to look into; of which the rock and manna, the brasen serpent, passover, &c. are instances: but rather, as the word "law" signifies "doctrine", the doctrine of the Gospel may be meant; which contains mysteries in it, respecting the trinity of Persons in the Godhead, the person of Christ, his incarnation, sufferings and death; the blessings of grace through him; the doctrines of peace, pardon, righteousness, eternal life, and the resurrection of the dead; with many others.
(t) "revela oculos meos", Pagninus, Montanus, Musculus, Cocceius, Gejerus, Michaelis; "velamen detrahe oculis meis", Tigurine version.

Open - Enlighten my mind by the light of thy Holy Spirit, and dispel all ignorance and error. Behold - Those great and marvellous depths of Divine wisdom and goodness, and those profound mysteries of Christ, and God's grace to mankind, and of that everlasting state, which are not to be known but by Divine illumination.