Because of his sin man has no means of salvation outside the cross.
Nevertheless knowing that a man is not justified by the works of the Law but through faith in Christ Jesus, even we have believed in Christ Jesus, so that we may be justified by faith in Christ and not by the works of the Law; since by the works of the Law no flesh will be justified (Gal 2:16; cf. Isa 64:6; Rom 3:19-20; Jas 2:10).
Reconciliation with God comes only through Christ’s death on the cross.
For He Himself is our peace, who made both groups into one and broke down the barrier of the dividing wall, by abolishing in His flesh the enmity, which is the Law of commandments contained in ordinances, so that in Himself He might make the two into one new man, thus establishing peace,and might reconcile them both in one body to God through the cross, by it having put to death the enmity (Eph 2:14-16; cf. Acts 20:28; Rom 5:1-11; 1 Cor 2:2; 2 Cor 5:18-21; Col 1:20-22).
Christ’s death on the cross was a propitiation (substitutionary sacrifice) to avert God’s wrath toward our sin.
For all have sinned and fall short of the glory of God, being justified as a gift by His grace through the redemption which is in Christ Jesus; whom God displayed publicly as a propitiation in His blood through faith. This was to demonstrate His righteousness, because in the forbearance of God He passed over the sins previously committed; for the demonstration, I say, of His righteousness at the present time, so that He would be just and the justifier of the one who has faith in Jesus (Rom 3:23-26; cf. Heb 2:17; 1 John 1:7; 2:2; 4:10).
Because of Christ’s death the debt of our sin was nailed to the cross.
When you were dead in your transgressions and the uncircumcision of your flesh, He made you alive together with Him, having forgiven us all our transgressions, having canceled out the certificate of debt consisting of decrees against us, which was hostile to us; and He has taken it out of the way, having nailed it to the cross (Col 2:13-14; cf. 1 Pet 2:24).
Salvation is not based on good deeds, but on the mercy of God.
But when the kindness of God our Savior and His love for mankind appeared, He saved us, not on the basis of deeds which we have done in righteousness, but according to His mercy, by the washing of regeneration and renewing by the Holy Spirit, whom He poured out upon us richly through Jesus Christ our Savior, so that being justified by His grace we would be made heirs according to the hope of eternal life (Titus 3:4-7).
Salvation comes only through faith in Christ’s substitutionary death, freely given by God’s grace.
For by grace you have been saved through faith; and that not of yourselves, it is the gift of God; not as a result of works, so that no one may boast (Eph 2:8-9).
Through faith in Christ, His righteousness is imputed to our account, making us acceptable to God.
For what does the Scripture say? “ABRAHAM BELIEVED GOD, AND IT WAS CREDITED TO HIM AS RIGHTEOUSNESS.” Now to the one who works, his wage is not credited as a favor, but as what is due. But to the one who does not work, but believes in Him who justifies the ungodly, his faith is credited as righteousness, just as David also speaks of the blessing on the man to whom God credits righteousness apart from works: “BLESSED ARE THOSE WHOSE LAWLESS DEEDS HAVE BEEN FORGIVEN, AND WHOSE SINS HAVE BEEN COVERED (Rom 4:3-7).