Through the lens of the truth of eternal security:
Matt 5:29 is teaching the concept of rebound for the believer. And it is a witnessing tool for us for the unbeliever.
A believer recognizes(cuts out his eye) his sin and names and sites it to God. And we are again back in fellowship.
An unbeliever recognizes(cuts out his eye) that they are a sinner in need of salvation, and trusts in Christ's person and work on the cross for them......saving them from hell.
Matt 5:19. If believers grieve and quench the Spirit and never get back into fellowship with Him(1 John 1:9).........they will be least in His Kingdom.
This is client nation status, not individual salvation. Israel had the duty of spreading the Gospel. God protected and blessed them so His word could advance. Israel stopped advancing His word, so He went to the Gentiles and Israel was cut off from being Gods client nation. He didn't cut off individual salvation.
This is physical death, and severe discipline. If we live outside of Gods plan for us we can expect discipline and possibly very severe discipline at that......physical death.
1 Cor 11:30~~
New American Standard Bible
For this reason many among you are weak and sick, and a number sleep.
Fellowship. The moment we believe we are Justified and will not come into judgement(forgiven.)
As believers, when we do sin, we lose fellowship. 1 John 1:9 is Gods mechanism for the believer to get back into fellowship with Him.
If you look at the NASB or KJV of 1 John 3:15 they have the word 'abiding.'
menó: to stay, abide, remain
Original Word: μένω
Part of Speech: Verb
Transliteration: menó
Phonetic Spelling: (men'-o)
Short Definition: I remain, abide
Definition: I remain, abide, stay, wait; with acc: I wait for, await.
In this particular verses 'abiding' is in the active voice. A brother who hates his brother is actively not abiding in eternal life. This is where we need to pay attention. It is a choice. These Brothers are not abiding in something they already have......their eternal life. An unbeliever does not have the choice to abide or not abide in eternal life.
This verse is not saying that they don't have eternal life. It is saying they are not abiding in what they DO have......1 John 1:9 for them to start abiding in the sphere of their eternal life again.
Being a believer does not = disciple. Being a disciple requires salvation THEN lots of study,doctrine and being saturated in His ways.
We most certainly have to obey to demonstrate that we are His disciples. Just that today, most just demonstrate that they are stuck at start and never even get their salvation figured out, let alone become His disciple.
They may look good to us, and counterfeit a lifestyle.......but their doctrines reveal their true motives.