"For it is by grace you have been saved, through faith -- and this not from yourselves, it is the gift of God -- not by works, so that no one can boast" (Ephesians 2:8-9).
The New Testament is first and foremost a written testimony of God's grace -- it is by grace we have been saved.
The word grace can be defined as God's undeserved favor. When Adam and Eve fell, God was under absolutely no obligation to effect a means whereby mankind could be restored to fellowship. Just as the angels who rebelled received swift judgment, so too could Adam and Eve have received a similar judgment. Such a judgment would not have been inconsistent with God's holy nature -- a nature which cannot tolerate sin. This is grace: that God has bestowed forgiveness and eternal life on sinners who, instead of favor, deserve nothing less than immediate, eternal punishment and separation from God.
"He was despised and rejected by men, a man of sorrows, and familiar with suffering. Like one from whom men hide their faces He was despised, and we esteemed Him not. Surely He took up our infirmities and carried our sorrows, yet we considered Him stricken by God, smitten by Him, and afflicted. But He was pierced for our transgressions, He was crushed for our iniquities; the punishment that brought us peace was upon Him, and by His wounds we are healed" (Isaiah 53:3-4)
To suggest that God's grace was conditional, or that grace alone is not sufficient, is to insult God. Isaiah 53 is but one example of what God underwent -- through the Incarnation -- to achieve our salvation. That God Himself took on human form, walked among us and suffered as we suffer, and then died an excruciating death on a cross -- all for the purpose of redeeming lost humanity -- is an example of the magnitude and incomprehensibility of God's love.
Every cult denies God's grace by denying God's sacrifice. Each teaches that human works are a necessary requirement for individual salvation; as if to say that the price God paid was not truly adequate, and therefore God needs our help. Any such teaching is a counterfeit gospel -- a doctrine of demons. The true New Testament gospel, the gospel of grace, is that, "all have sinned and fall short of the glory of God, and are justified freely by his grace through the redemption that came by Christ Jesus" (Romans 3:23-24).
"So do not be ashamed to testify about our Lord, or ashamed of me His prisoner. But join with me in suffering for the gospel, by the power of God, who has saved us and called us to a holy life -- not because of anything we have done but because of His own purpose and grace" (2 Timothy 1:8-9).