Answer
Isaiah’s prophecies address not only God’s judgment but also God’s grace. In them God often refers to His earlier promises, as He does in Isaiah 54:9, saying, “For this is like the waters of Noah to me.” Though Israel had broken God’s (Mosaic) covenant and would soon undergo judgment (see chapters 1—3, for example), there would be a remnant and those who would see God’s restoration afterward (Isaiah 14, 27, for example). Isaiah 54:1–3 speaks of the nation having many descendants, enlarging their tent, spreading abroad, possessing nations, and resettling cities that had been desolate. The people would forget the shame of their former disobedience (Isaiah 54:4), because God has redeemed and called them (Isaiah 54:5). The people would not be restored because of their righteousness, but in spite of their unfaithfulness God would deliver them (Isaiah 54:6).
God had judged the people briefly but would with great compassion restore them (Isaiah 54:7). The nation had been judged for a moment but would see God’s everlasting kindness and compassion (Isaiah 54:8). Because of the temporality of God’s judgment and the eternality of His blessing, in this case God says that “this is like the waters of Noah to me” (Isaiah 54:9). In the days of Noah, human wickedness had reached such an apex that God would tolerate it no further and would bring judgment (Genesis 6:5–7) through a worldwide flood. But even in the midst of that judgment God would show His mercy as He chose to protect the line of Noah because of Noah’s righteousness (Genesis 6:8; 7:1). God brought Noah, his family, and representatives from the various animal families through the judgment (Genesis 7:17–24).
After the judgment through the flood, God made a covenant with Noah and with every living thing that He would never again destroy the earth with a flood (Genesis 9:11). Because of that earlier promise, God said in Isaiah 54:9 that the current judgment would be “like the waters of Noah to me.” God had sworn that waters of Noah (or judgment) would not flood the earth again (Genesis 9:11; Isaiah 54:9), and in the same way God was now telling the people that after the judgment they would encounter, He would no longer be angry or rebuke the people (Isaiah 54:9). Even though the mountains may be removed and the hills shaken, God would not remove His lovingkindness or allow His covenant of peace to be broken (Isaiah 54:10).
God is a holy, holy, holy God (Isaiah 6:3) who does not ignore His people’s sin. He had promised that if Israel would obey the covenant He gave them through Moses that they would dwell peacefully in the land (Exodus 19:5–6; Deuteronomy 28:1–15). But if they disobeyed God, they would be judged and removed from the land (Deuteronomy 28:16–66). Yet even after that judgment took place, God would restore the people (Deuteronomy 30). The judgment would not last forever. God’s judgment of Israel would be “like the waters of Noah” to God (Isaiah 54:9) in that it would be temporary and the people would be ultimately delivered.
In a similar way, we see God’s grace poured out on those who believe in Jesus Christ—even though we are worthy of an eternal penalty (death), God loves us and sent His Son Jesus to die as a substitution in our place. He took on Himself the penalty for Israel’s sin and for ours (Isaiah 53:4–12)—in fact, He died for the whole world (1 John 2:2) so that all who believe in Him can have eternal life (John 6:47; 20:31). For those who believe in this Savior, God’s judgment is “like the waters of Noah”—we were by nature children of wrath (Ephesians 2:3), but God has saved us by His mercy (Ephesians 2:4).