Here is what scripture list as spiritual sin that are the sins unto death.[1Jo 5:16 KJV] 16 If any man see his brother sin a sin [which is] not unto death, he shall ask, and he shall give him life for them that sin not unto death. There is a sin unto death: I do not say that he shall pray for it.
Pro 6:16 These six things doth the LORD hate: yea, seven are an abomination unto him:
Pro 6:17 A proud look, a lying tongue, and hands that shed innocent blood,
Pro 6:18 An heart that deviseth wicked imaginations, feet that be swift in running to mischief,
Pro 6:19 A false witness that speaketh lies, and he that soweth discord among brethren.
The spiritual sin unto death is willful, continuous, unrepented sin. No one who is Spiritually born again and indwelled with the Holy Spirit will willfully sin.
1John 5:16 If any man see his brother sin a sin which is not unto death, he shall ask, and he shall give him life for them that sin not unto death. There is a sin unto death: I do not say that he shall pray for it.
We can clearly see in 1John 5:16 it is not speaking about spiritual sin that are the sins unto death. There is willful sin that is taught in Hebrews 10 that bring about a certain fearful looking for of judgment and fiery indignation, which shall devour the adversaries.
Heb 10:26 For if we sin wilfully after that we have received the knowledge of the truth, there remaineth no more sacrifice for sins,
Heb 10:27 But a certain fearful looking for of judgment and fiery indignation, which shall devour the adversaries.
Heb 10:28 He that despised Moses' law died without mercy under two or three witnesses:
Heb 10:29 Of how much sorer punishment, suppose ye, shall he be thought worthy, who hath trodden under foot the Son of God, and hath counted the blood of the covenant, wherewith he was sanctified, an unholy thing, and hath done despite unto the Spirit of grace?
Jesus tasted death upon the cross so everyone could have an opportunity to turn away from their willful sinning if they would truly turn from spiritual sin unto death with a heart of repentance and become Spiritually born again in order to inherit the kingdom of God.
There are five requirements to Salvation
1. Confession - Acts 2:21; Romans 10:9, 10
2. Repentance - Mark 1:14, 15
3. Faith - John 3:14-18
4. Regeneration - John 3:3-8
5. Holy Scripture - 2 Timothy 3:15