You look, brethren, lest there is in any among you a malignantly evil heart of unbelief in departing from [the] living God, but encourage yourselves according to each day, as far as it is called today, in order that no one out from you is hardened by the deceit of the sin, Hebrews 3:12–13.
“Today, if you will hear my voice.” Paul encourages the Christians in Jerusalem not to follow the path of their fathers, who tempted God and saw His works for forty years until that generation passed away. For God swore in His wrath that they would not enter into His rest (Hebrews 3:7–10).
Let us not harden our hearts, being deceived by our sin nature, but instead let us enter into His rest. This is not a seventh-day rest from our works to maintain righteousness, but a seven-day rest because we are now righteous in Christ. Christ is the author and finisher of our faith, for in Him we are complete (Hebrews 12:2). Therefore, let us not turn again to dead works; instead, let us walk in the newness of life we have in Christ (Romans 6:4).
The hardening of the heart happens when we reject the truth and seek to establish our own righteousness through works, not submitting to the righteousness of God (Romans 10:3). The Christian life is not lived out through law, but through the freedom we have in Christ to live out the righteousness in Christ we now possess. Therefore, since we are the chosen of God, let us put on Christ as our outer garment. This is done by recognizing that our life is now hidden in Christ, for He is our sanctification and righteousness (Colossians 3:3; 1 Corinthians 1:30). We belong to Him. Our life is no longer our own, but the life we now live, we live in the faith of His Son, who loved us and gave Himself for us (Galatians 2:20).