isaiah 64:4 For since the beginning of the world men have not heard, nor perceived by the ear, neither hath the eye seen, O God, beside thee, what he hath prepared for him that waiteth for him. - Free Bible Online

      4. perceived by the ear--Paul (1Co 2:9) has for this, "nor have entered into the heart of man"; the virtual sense, sanctioned by his inspired authority; men might hear with the outward ear, but they could only by the Spirit "perceive" with the "heart" the spiritual significancy of God's acts, both those in relation to Israel, primarily referred to here, and those relating to the Gospel secondarily, which Paul refers to.
      O God . . . what he . . . prepared--rather, "nor hath eye seen a god beside thee who doeth such things." They refer to God's past marvellous acts in behalf of Israel as a plea for His now interposing for His people; but the Spirit, as Paul by inspiration shows, contemplated further God's revelation in the Gospel, which abounds in marvellous paradoxes never before heard of by carnal ear, not to be understood by mere human sagacity, and when foretold by the prophets not fully perceived or credited; and even after the manifestation of Christ not to be understood save through the inward teaching of the Holy Ghost. These are partly past and present, and partly future; therefore Paul substitutes "prepared" for "doeth," though his context shows he includes all three. For "waiteth" he has "love Him"; godly waiting on Him must flow from love, and not mere fear.

JFB.