"To me this is like the days of Noah, when I swore that the waters of Noah would never again cover the earth. So now I have sworn not to be angry with you, never to rebuke you again. Though the mountains be shaken and the hills be removed, yet my unfailing love for you will not be shaken nor my covenant of peace be removed," says the LORD, who has compassion on you.
But how is it that God can promise to never again be angry or rebuke again? For what about recidivism? What if the redeemed turn away again and sin? The New Testament gives much correction and rebuke and warning to those who are nonetheless reckoned redeemed. In fact discipline is part of the Christian life as he says, "My son, do not make light of the Lordís discipline, and do not lose heart when he rebukes you, because the Lord disciplines those he loves, and he punishes everyone he accepts as a son." Endure hardship as discipline; God is treating you as sons. For what son is not disciplined by his father? Heb 12:5-7 Therefore it seems this promise in Isaiah is not referring to this present dispensation, but rather one in which sanctification will be perfected. For salvation incorporates not simply the forgiveness of sins, but also the removal of one's innate sinfulness.
Notice for example how the Bible speaks of Christ's work of sanctification as husband to the Church. "Husbands, love your wives, just as Christ loved the church and gave himself up for her to make her holy, cleansing her by the washing with water through the word, and to present her to himself as a radiant church, without stain or wrinkle or any other blemish, but holy and blameless." Eph 5:21-27 Thus by the wedding feast of the Lamb God's people will be perfectly sanctified.Notice also that he mentions a dispensational event here in Isaiah 54:9 - the waters of Noah. The reconciliation of the remnant of Israel will be fully realized at the dispensational event we find near the end of the book of Revelation initiating the Millenial Kingdom - the wedding feast of the Lamb. Then concerning the new order to come it is written, "I saw the Holy City, the new Jerusalem, coming down out of heaven from God, prepared as a bride beautifully dressed for her husband. And I heard a loud voice from the throne saying, "Now the dwelling of God is with men, and he will live with them. They will be his people, and God himself will be with them and be their God. He will wipe every tear from their eyes. There will be no more death or mourning or crying or pain, for the old order of things has passed away." Rev 21:2-4