Ephesians 2:8-9 ASV
(8) for by grace have ye been saved through faith [belief, trust]; and that not of yourselves, it is the gift of God;
(9) not of works, that no man should glory.
WHY IS SALVATION IS INDEED A FREE GIFT?
To understand why salvation is free we must be able to grasp what we call sin is and the IRREVERSIBLE consequence of sin.
Sin has been a disagreement with what God commands and remains the same forever even after the end of the world. That is why we each must prove to God here on earth that we would rather die here on earth than disagree with Him no matter what we are facing. That is the tenor of Matthew 6:10: 'Your will be done on earth as in heaven'. In other words God wants zero disagreement (sin) from mankind to qualify for take advantage of the offer of the gift.
What is the punishment for disagreeing (sinning) with God. Irreversible death, as attested by the fate of the fallen angels and those who follow their rebellion or disobedience.
For whatever reason, according to Jesus, out of love for His own Image, God designed the plan of salvation to give man another chance at immortality. How would God fare in the shoes of man, God might have asked Himself? Then, God Father chose YHWH God and presented the plan to YHWH God for its execution who naturally (heavenlily??) agree (John 10:17-18).
If Jehovah God would have failed, man would have be doomed forever for destruction with Satan and God would have been left with no remembrance of His other Image, man, whom they fashioned at Their own Image. That was too much for the Father to bear.
Adam and Eve must have repented after they realized that God was right and Satan was wrong. Their repentance meant nothing apart from the successful completion of the plan of salvation by YHWH God way after the first sin. Because there is no contrition from man that could have changed the outcome of sin, salvation becomes a gift to those who want to sign up for the successful completion of the plan as Jesus did complete it. The difference is that Jesus just as Adam had one chance but that we have multiple tries until we overcome (Revelation 3:20-21).
Overcoming for salvation (Revelation 3:20-12) requires works of struggles, failures, and victory. Salvation does not initiate those struggles, the hope of salvation (1 Thessalonians 5:8) does because salvation is hope, promise (2 Thessalonians 5:8, 1 Peter 1:13), not something tangible yet.
According to Ezekiel 33:13, we can lose that hope if we get blinded by it by not working it out with fear and trembling (Philippians 2:12).
Salvation takes so much work that, in Philippians 2:12, Apostle Paul counsels us to work out our salvation with fear and trembling.
Philippians 2:12 ASV
(12) So then, my beloved, even as ye have always obeyed, not as in my presence only, but now much more in my absence, work out your own salvation with fear and trembling;
It is claimed that those who attempt to save themselves by keeping the law will fail in their efforts. But Ezekiel 33:13, James 2:10, John 14:21-23, et cetera, contradict that claim that keeping the law will not save us because not keeping the law 100% will cause us to die and to be tormented day and night in the lake of fire with Satan.
When we repented, our sins were forgiven to become holy as the commandment of holiness wants us to be and our sins were paid for until we sin again. At baptism, we became holy, sanctified (sanctification in which we must live and die in righteousness) to be then sanctified if we overcame with the stamp of approval of the grace of God.
Apostle Paul teaches that we believe to become righteous (Romans 10:10-11) by living in holiness which is attained by keeping all the commandments of Jesus God according to Numbers 25:40.
Apostle Paul teaches that one ONE thing saves or that salvation is obtained by one thing: confession wit our own mouth that Jesus is YAHWEH ELOHIM in the flesh of Jesus. Romans 10:10
Romans 10:10 ASV
(10) for with the heart man believeth unto righteousness; and with the mouth confession is made unto salvation.