Just one act of disobedience led to Adam and Eve's spiritual death. Eternal security proponents say that believers cannot die spiritually over any sin, which is the same lie Satan told Eve. Genesis 3:3-4 But of the fruit of the tree which is in the midst of the garden, God hath said, Ye shall not eat of it, neither shall ye touch it, lest ye die. [4] And the serpent said unto the woman, Ye shall not surely die:
Genesis 7:1, 7-10
1 And the LORD said unto Noah, Come thou and all thy house into the ark; for thee have I seen righteous before me in this generation.
7 And Noah went in, and his sons, and his wife, and his sons' wives with him, into the ark, because of the waters of the flood.
8 Of clean beasts, and of beasts that are not clean, and of fowls, and of every thing that creepeth upon the earth,
9 There went in two and two unto Noah into the ark, the male and the female, as God had commanded Noah.
10 And it came to pass after seven days, that the waters of the flood were upon the earth.
If Noah refused to build the ark, would he have been saved? What if he jumped out of the ark would he have still been saved? No. Simple obedience was all that was necessary to be kept safe during the flood. Likewise, abiding in Christ, making our election sure, diligence in the faith, and obedience to God guarantees eternal salvation (Hebrews 5:9).
King David did not have to commit adultery and murder habitually before becoming an adulterer and murderer. Just one act made him an adulterer and murderer and brought him under guilt and condemnation. Galatians 5:19-21
19 Now the works of the flesh are manifest, which are these; Adultery, fornication, uncleanness, lasciviousness,
20 Idolatry, witchcraft, hatred, variance, emulations, wrath, strife, seditions, heresies,
21 Envyings, murders, drunkenness, revellings, and such like: of the which I tell you before, as I have also told you in time past, that they which do such things shall not inherit the kingdom of God. Eternal security doctrine says "believers who do such things shall inherit the kingdom of God but lose rewards", so if David did not repent he will still inherit the kingdom but lose rewards for his sins. This doctrine completely redefines the gospel message in which one’s justification is disconnected from their conduct thus grace has been reduced to a get-out-of-hell free ticket plus a license to sin, and obedience to God by His grace is regarded as works salvation. On the contrary, the true grace of God teaches us that, denying ungodliness and worldly lusts, we should live soberly, righteously, and godly in this present world (Titus 2:12).
When the prodigal son was living riotously and wandering in the pigsty he was spiritually dead. However, eternal security proponents turn a blind eye to this passage and say that he was still alive in the pigsty, saved whilst in captivity of sin: Luke 15:24 For this my son was dead, and is alive again; he was lost, and is found. And they began to be merry.
Nowhere in the bible does it say believers can live like the world and remain in a justified state. James said that one who is conforming to worldliness is committing spiritual adultery (unfaithfulness) and is an enemy of God. Enemies of God will not spend eternity with Him, but with their master, the devil, who is also an enemy of God. James 4:4 Ye adulterers and adulteresses, know ye not that the friendship of the world is enmity with God? whosoever therefore will be a friend of the world is the enemy of God.