2 Corinthians 3:14
But their minds were blinded: for until this day remaineth the same vail untaken away in the reading of the old testament; which [vail] is done away in Christ.
Note 13 at 2Co 3:14: "Blindness" is used metaphorically in the Scriptures to portray spiritual insensitivity. The Greek word "POROO," translated "blinded" here, was translated "hardened"--i.e., a hardened heart--three times (Mr 6:52, 8:17; and Joh 12:40) and "blinded"--i.e., spiritual blindness--two times (Ro 11:7 and this verse). POROO carries the idea not only of losing the power to perceive and understand, but also the idea of hardening as by a callus. Trying to relate to the Lord on the basis of Law blinds us or hardens our hearts to the true revelation of God's grace (see note 14 at this verse).
Note 14 at 2Co 3:14: Just as a physical veil was upon Moses' face, Paul was saying that a spiritual veil was over Israel's minds and hearts until this day (Isa 53:1-3; Ro 3:1-3, 11:7, and 25). This veil blinded Israel to the true meaning of many Old Testament scriptures that spoke of the grace and mercy of the New Covenant.
Jesus said to His unbelieving disciples, "These are the words which...must be fulfilled, which were written in the law of Moses, and in the prophets, and in the psalms, concerning me. Then opened he their understanding, that they might understand the scriptures" (Lu 24:44-45). Jesus removed the veil from their understanding.
Those who are trying to obtain righteousness through their actions (Law) have a veil over their understanding. Legalistically minded people do not understand the grace of God. However, when they turn to the grace that is in Christ Jesus, the spiritual veil of unbelief is removed. A revelation of righteousness by grace opens up the Scriptures as no other revelation does.