Jeremiah 5:21 → Isaiah 6:9-10

Isaiah's inaugural commission seals the substance of Judah's coming judgment into a perceptive triad — "Be ever hearing, but never understanding; be ever seeing, but never perceiving" (Isa 6:9), the prophet himself commanded to "deafen their ears and close their eyes" (6:10). Jeremiah, prophesying to a later generation on the eve of Babylon, reaches back to that same template: "Hear this, O foolish and senseless people, who have eyes but do not see, who have ears but do not hear" (Jer 5:21). The shared diagnostic is the paired faculties of eyes/see and ears/hear — organs of revelation present and functioning, yet judicially shut to perception. This is not a quotation but an Allusion: Jeremiah does not cite Isaiah by formula; he reapplies the fixed verbal pattern Isaiah supplied, indicting his own generation by the prophetic vocabulary already established. The connection is best read as a Longitudinal Theme — the judicial-hardening / perceptive-triad motif that runs Deuteronomy 29:2-4 → Isaiah 6:9-10 → Jeremiah 5:21 → Ezekiel 12:2 — rather than typology, since no antitype escalates a type; and as Redemptive-Historical Progression, the same hardening-indictment advancing down the line of writing prophets to the exilic crisis. The road to Christ runs through the NT's fourfold citation of Isaiah 6 (Matt 13; Mark 4; John 12; Acts 28), where this very triad interprets why Israel rejects her Messiah — and supremely through John 12:41, which testifies that Isaiah saw His glory and spoke of Him. The hardening line ends not in despair but in the One who opens blind eyes and unstops deaf ears (Isa 35:5): the dullness Jeremiah names is the precise lack that Christ alone supplies, so that to behold Him is to receive at last the seeing-and-hearing the prophets longed to grant — and to find that sight is itself the sweetness, the unveiled face transformed with intensifying glory.