Twice in Isaiah 40 the question is asked about things we have not known or heard (Isaiah 40:21, 28). The first appearance of the question is in Isaiah 40:21:
Have you not heard?
Has it not been told you from the beginning?
Have you not understood from the foundations of the earth?” (NKJV).
Isaiah’s fourfold question is rhetorical. Of course, they had known; of course, they had heard that it is God alone
And its inhabitants are like grasshoppers,
Who stretches out the heavens like a curtain,
And spreads them out like a tent to dwell in.
He brings the princes to nothing;
He makes the judges of the earth useless” (Isaiah 40:22–23, NKJV).
The point is that no one is God’s equal (Isaiah 40:18, 25). Isaiah’s readers have known and heard, and it matters because God is the Creator and Sovereign over all. Thus, all are accountable to Him. Idolatry—the worship of false gods—is foolish (verses 19–20).
Isaiah adds that God controls the weather and has created, numbered, and named the stars (Isaiah 40:24, 26). Isaiah reminds his readers that, if God is in control of nature to this extent, then what they have known and heard does indeed matter. They should not think that their way is hidden from God or that they would escape justice (Isaiah 40:27).
Later in the same passage, Isaiah asks again, “Do you not know, have you not heard?” (Isaiah 40:28a). The point this time is that the Creator has unlimited strength and wisdom:
the Creator of the ends of the earth.
He will not grow tired or weary,
and his understanding no one can fathom” (Isaiah 40:28b)
He is the One who, in His mercy, strengthens those who have no strength (Isaiah 40:29). Even those who have strength might stumble (Isaiah 40:30), but those who wait on Him will be strengthened (Isaiah 40:31).
The people had known and heard the truth; it had been declared to them from the beginning, even from the foundations of the earth. As Paul would later explain, God has revealed Himself through all that He has made, showing His invisible attributes, eternal power, and divine nature (Romans 1:20). Through His creation God has shown enough of Himself that all people are without excuse (Romans 1:20). We have known and heard, and it does matter. As Isaiah explains, God shows through His sovereignty over nature that all people are accountable to Him. To those who will depend on Him, God will give strength to soar, run, and walk without being weary.
God has revealed Himself through what He has made. We have known and heard. While this natural revelation is sufficient for all people (no one can claim he didn’t know about God), God has revealed much more detail about Himself in His Word and through Jesus Christ. In fact, we are told that the way we receive the grace of God leading to righteousness is by faith in Jesus Christ. We are all accountable to God. He asks us to believe in Jesus.
Imagine, the sovereign Creator of all simply asks us to put our trust (or faith) in Him so that we can have a new relationship with Him and eternal life. Like us, Isaiah’s audience needed to understand that they were accountable to God and that He is the One who could provide what they needed. They had known and heard. Now they needed to act on what they knew.
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