The phrase sea of forgetfulness is not actually in Scripture. When people mention the “sea of forgetfulness,” they are usually referring to several passages that talk about God’s forgiveness, and how when we are justified in Christ, God forgets our sins so completely that they might as well be buried at the bottom of an ocean.
The main passage that contains the idea of a sea of forgetfulness is Micah 7:19: “He will again have compassion on us, and will subdue our iniquities. You will cast all our sins into the depths of the sea.” Another verse, Isaiah 1:18, says that God will make our scarlet sins as white as wool. Psalm 103:12 expresses the thought in yet another way: “As far as the east is from the west, so far has He removed our transgressions from us.”
A sea of forgetfulness represents a place where our sins are sent very far away from us, so that they can no longer affect us. It does not mean that we, as believers, no longer sin or that our sins are erased from God’s mind. It only means that our sins no longer have any bearing on our salvation. Jesus’ perfect life, sacrificial death, and glorious resurrection is the only means by which we are saved (Acts 4:12). When we trust in Christ, we come under a new paradigm. Although our sins still grieve God and cause ruin in our lives and in the lives of others, our salvation is secure (Romans 8:1, 31–39).
The idea that our sins are lost in a sea of forgetfulness is a comfort. We are no longer judged by our sins (Romans 8:1), and that fact frees us to live life in a way that pleases God. When we fear judgment, ironically, we are tempted to sin even more, because we want to escape from the fear of judgment, and sin is often pleasurable for a time (see Hebrews 11:25). But, eventually, the fear of judgment returns. This is a vicious cycle. Spiritual growth requires that we recognize the total forgiveness that exists in Jesus Christ and that we rest in that forgiveness.
Many people do not believe they require salvation. They believe that they are good enough to reach heaven on their own merit, and they do not accept the truth about their own fallen state. These people are deceived, and they do not have a relationship with God (1 John 1:8, 10). Every person needs God’s forgiveness and salvation—a relationship based on dependence on His grace. If we admit that we are sinners and trust in Christ, He forgives and cleanses us (1 John 1:9). Our sins are no longer part of the equation and will not be remembered (Jeremiah 31:34; Hebrews 8:12).