Why is faith important for entering God's rest?

Faith is vital for entering into the rest that God provides because, as Hebrews 4:2 indicates, the gospel proclaimed must be mixed with faith to be effective. Our faith acknowledges our inability to achieve righteousness on our own and instead rests in the complete work of Christ. This faith results in a profound assurance that we are accepted by God, not because of our merits but through Christ's atoning sacrifice. Therefore, the act of believing in Christ is what brings us into the promise of God's rest, where we cease from striving to justify ourselves.