I agree. But it seems rather obvious. If we are saved by grace through faith, then we can lose salvation by apostasy.
The question of whether certain sins lead to death if not confessed makes me wonder if a murderer who doesn't repent could be saved, because they would surely be grieving the Spirit. But I don't know, so I'm not going to claim to know what sin ( other than unbelief) is unforgivable. As far as I can tell, only final rejection of the Spirit is.
The Bible’s teaching that serious sin is separation from GOD:
[God said to Adam,]
"But of the tree of the knowledge of good and evil, thou shalt not eat of it: for in the day that thou eatest thereof thou shalt surely die." (Genesis 2:17).
[Eve said to the serpent,]
"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. (Genesis 3:3).
And the serpent said unto the woman,
"Ye shall not surely die." (Genesis 3:4).
"...she took of the fruit thereof, and did eat, and gave also unto her husband with her; and he did eat. And the eyes of them both were opened, and they knew that they were naked..." (Genesis 3:6-7).
"Wherefore, as by one man sin entered into the world, and death by sin; and so death passed upon all men, for that all have sinned." (Romans 5:12).
"For the wages of sin is death..." (Romans 6:23).
"But your iniquities have separated between you and your God, and your sins have hid his face from you, that he will not hear." (Isaiah 59:2).
“...whosoever shall say, Thou fool, shall be in danger of hell fire.” (Matthew 5:22).
28 “But I say unto you, That whosoever looketh on a woman to lust after her hath committed adultery with her already in his heart.
29 And if thy right eye offend thee, pluck it out, and cast it from thee: for it is profitable for thee that one of thy members should perish, and not that thy whole body should be cast into hell.
30 And if thy right hand offend thee, cut it off, and cast it from thee: for it is profitable for thee that one of thy members should perish, and not that thy whole body should be cast into hell.” (Matthew 5:28-30).
"But whoso committeth adultery with a woman lacketh understanding: he that doeth it destroyeth his own soul." (Proverbs 6:32).
“But if ye forgive not men their trespasses, neither will your Father forgive your trespasses.” (Matthew 6:15).
“Not every one that saith unto me, Lord, Lord, shall enter into the kingdom of heaven; but he that doeth the will of my Father which is in heaven.” (Matthew 7:21)
Important Note: If you were to look at 1 Thessalonians 4:3 you would learn that the will of God (i.e. the Father) is to be holy or it is our sanctification; And Hebrews 12:14 says, without holiness no man shall see the Lord.
“22 On that day many will say to me, ‘Lord, Lord, did we not prophesy in your name, and cast out demons in your name, and do many mighty works in your name?’
23 And then will I declare to them, ‘I never knew you; depart from me, you workers of lawlessness.’” (Matthew 7:22-23 ESV).
“26 And every one that heareth these sayings of mine, and doeth them not, shall be likened unto a foolish man, which built his house upon the sand:
27 And the rain descended, and the floods came, and the winds blew, and beat upon that house; and it fell: and great was the fall of it.”
(Matthew 7:26-27).
“15 Beware of false prophets, which come to you in sheep's clothing, but inwardly they are ravening wolves.
16 Ye shall know them by their fruits. Do men gather grapes of thorns, or figs of thistles?
17 Even so every good tree bringeth forth good fruit; but a corrupt tree bringeth forth evil fruit.
18 A good tree cannot bring forth evil fruit, neither can a corrupt tree bring forth good fruit.
19 Every tree that bringeth not forth good fruit is hewn down, and cast into the fire.
20 Wherefore by their fruits ye shall know them.” (Matthew 7:15-20).
"For if we sin wilfully after that we have received the knowledge of the truth, there remaineth no more sacrifice for sins." (Hebrews 10:26).
"he that commits sin is of the devil." (1 John 3:8).
"everyone who does evil hates the light." (John 3:20).
"Repent therefore of this thy wickedness, and pray God, if perhaps the thought of thine heart may be forgiven thee." (Acts of the Apostles 8:22).
6 "If we say that we have fellowship with him, and walk in darkness, we lie, and do not the truth.
7 But if we walk in the light, as he is in the light, we have fellowship one with another, and the blood of Jesus Christ his Son cleanseth us from all sin." (1 John 1:6-7).
"He that saith, I know him, and keepeth not his commandments, is a liar, and the truth is not in him." (1 John 2:4).
"Whosoever hateth his brother is a murderer: and ye know that no murderer hath eternal life abiding in him." (1 John 3:15).
"He that saith he is in the light, and hateth his brother, is in darkness even until now." (1 John 2:9).
"In this the children of God are manifest, and the children of the devil: whosoever doeth not righteousness is not of God, neither he that loveth not his brother." (1 John 3:10).
41 "The Son of Man will send his angels, and they will gather out of his kingdom all causes of sin and all law-breakers,
42 and throw them into the fiery furnace. In that place there will be weeping and gnashing of teeth.
43 Then the righteous will shine like the sun in the kingdom of their Father. He who has ears, let him hear." (Matthew 13:41-43 ESV).
“For by thy words thou shalt be justified, and by thy words thou shalt be condemned.” (Matthew 12:37).
"They profess that they know God; but in works they deny him, being abominable, and disobedient, and unto every good work reprobate." (Titus 1:16).
3 "If any man teach otherwise, and consent not to wholesome words, even the words of our Lord Jesus Christ, and to the doctrine which is according to godliness;
4 He is proud, knowing nothing,..." (1 Timothy 6:3-4).
"...God resisteth the proud, but giveth grace unto the humble."
(James 4:6).
21 For if God spared not the natural branches, take heed lest he also spare not thee.
22 Behold therefore the goodness and severity of God: on them which fell, severity; but toward thee, goodness, if thou continue in his goodness: otherwise thou also shalt be cut off." (Romans 11:21-22).
16 "There is a sin unto death..."
17 "...and there is a sin not unto death." (1 John 5:16-17).
"But the fearful, and unbelieving, and the abominable, and murderers, and whoremongers, and sorcerers, and idolaters, and all liars, shall have their part in the lake which burneth with fire and brimstone: which is the second death." (Revelation 21:8).
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." (Galatians 5:19-21).
5 "Mortify therefore your members which are upon the earth; fornication, uncleanness, inordinate affe
ction, evil concupiscence, and covetousness, which is idolatry:
6 For which things' sake the wrath of God cometh on the children of disobedience:
7 In the which ye also walked some time, when ye lived in them." (Colossians 3:5-7).
5 “...God;
6 ...will render to every man according to his deeds:
7 To them who by patient continuance in well doing seek for glory and honour and immortality, eternal life:
8 But unto them that are contentious, and do not obey the truth, but obey unrighteousness, indignation and wrath,
9 Tribulation and anguish, upon every soul of man that doeth evil, of the Jew first, and also of the Gentile;
10 But glory, honour, and peace, to every man that worketh good, to the Jew first, and also to the Gentile:
11 For there is no respect of persons with God.
12 For as many as have sinned without law shall also perish without law: and as many as have sinned in the law shall be judged by the law” (Romans 2:5-12).
“But when the righteous turneth away from his righteousness, and committeth iniquity, and doeth according to all the abominations that the wicked man doeth, shall he live? All his righteousness that he hath done shall not be mentioned: in his trespass that he hath trespassed, and in his sin that he hath sinned, in them shall he die.” (Ezekiel 18:24).
9 “Know ye not that the unrighteous shall not inherit the kingdom of God? Be not deceived: neither fornicators, nor idolaters, nor adulterers, nor effeminate, nor abusers of themselves with mankind,
10 Nor thieves, nor covetous, nor drunkards, nor revilers, nor extortioners, shall inherit the kingdom of God. “ (1 Corinthians 6:9-10).
“Even so faith, if it hath not works, is dead, being alone.” (James 2:17).
"And cast ye the unprofitable servant into outer darkness: there shall be weeping and gnashing of teeth." (Matthew 25:30).
“For if ye live after the flesh, ye shall die: but if ye through the Spirit do mortify the deeds of the body, ye shall live.” (Romans 8:13).
