God gave the Old Testament to Israel,which if any person did not abide by that was cut off from that covenant,and the Gentiles could take hold of that covenant,but if later on they did not abide by it then they would be cut off.
God gave the New Testament to Israel,which Gentiles can take hold of that covenant,and when they accept that covenant,if they do not abide by it later on,then they will be cut off.
If they do not correct themselves,they will be cut off.
The same rule applies if you accept that covenant as a Gentile in either covenant,and did not comply later on,and correct yourself,then you will be cut off,which Jesus addressed the Churches in Revelation,and told them to repent,they have fallen,and their works were not found perfect before God,and if they did not repent then they would be cut off.
Rom 11:16 For if the firstfruit be holy, the lump is also holy: and if the root be holy, so are the branches.
Rom 11:17 And if some of the branches be broken off, and thou, being a wild olive tree, wert graffed in among them, and with them partakest of the root and fatness of the olive tree;
Rom 11:18 Boast not against the branches. But if thou boast, thou bearest not the root, but the root thee.
Rom 11:19 Thou wilt say then, The branches were broken off, that I might be graffed in.
Rom 11:20 Well; because of unbelief they were broken off, and thou standest by faith. Be not highminded, but fear:
Rom 11:21 For if God spared not the natural branches, take heed lest he also spare not thee.
Rom 11:22 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.
The same rule applies in the Old,and New,abide by the covenant or you will be cut off,and that cutting off is explained,for they did not continue in God's goodness,being Christlike,so we see what is important to the New Testament covenant,represent goodness.
Heb 3:7 Wherefore (as the Holy Ghost saith, To day if ye will hear his voice,
Heb 3:8 Harden not your hearts, as in the provocation, in the day of temptation in the wilderness:
Heb 3:9 When your fathers tempted me, proved me, and saw my works forty years.
Heb 3:10 Wherefore I was grieved with that generation, and said, They do alway err in their heart; and they have not known my ways.
Heb 3:11 So I sware in my wrath, They shall not enter into my rest.)
Heb 3:12 Take heed, brethren, lest there be in any of you an evil heart of unbelief, in departing from the living God.
Heb 3:13 But exhort one another daily, while it is called To day; lest any of you be hardened through the deceitfulness of sin.
Here is another example of those Jews in the Old Testament that would not abide,that they were cut off,and warns the Gentiles that they should not go back to unbelief,in departing from the living God,and how did they do that,by not continuing in the goodness of God,for they were hardened through the deceitfulness of sin.
Which how many people actually repented of their sins to start with,for the relaxed attitude that many have,did they truly repent,and want to represent goodness,or when they confessed Christ did they have the attitude sin does not affect their relationship with God,and did not make an attempt to try to rid themselves of all their sins,but held unto some,or toned it down a bit,but only was covering their past sins,but did not want to get rid of what was currently going on with sin in their life.
If people that did start in God's goodness,but later on went to some sinful ways,and if they do not correct themselves will be cut off,where does that leave people that did not even make an effort to represent goodness,at least not totally,with the relaxed preaching of the Church telling them you cannot beat sin,and it does not affect your relationship with God.
Did they truly repent.
They have been chosen in the beginning,and cannot fall no matter what,is the whole basis of their belief,and not even scriptures can shake them from that belief.
If you do not continue in God's goodness,you will be cut off,but did they start in God's goodness,and they will depart from the living God,if later on they harden their heart by the deceitfulness of sin,but did they start to cease from all sin.
If they say they cannot abstain from sin,and sin does not affect their relationship with God,how could they of truly repented of their sins,when it means you do not want to sin in the future,for it is a turning away from sin.