2. The Scripture which states it is possible to believe for a while and stop believing is Luke 8:13. It says:
They believe for a while, but in the time of testing they fall away.
3. Gal. 5:2-4 shows one can fall from grace, which is the same as Christ being of no benefit to you at all. Were the ones who fell from grace (the Galatians, who were trying to be justified by law) previously saved? Absolutely. Here is the proof:
They had believed and received the true gospel (3:2; 1:9); were deserting God and turning to a false gospel (1:6); had received the Spirit of God (3:2,5); were initially running a good spiritual race (5:7); etc. Compare this to Acts 14:21-23 which also shows the Galatians became disciples, were in the Christian faith (at that time), and placed their trust in the Lord.
4. A covenant can be broken. Here is clear Biblical proof:
Like Adam, they have broken the covenant—they were unfaithful to me there. (Hosea 6:7)
(NOTE: Adam broke the covenant through sin and died spiritually.)
It will not be like the covenant I made with their forefathers when I took them by the hand to lead them out of Egypt, because they did not remain faithful to my covenant, and I turned away from them, declares the Lord. (Heb 8:9)
I prayed to the LORD my God and confessed: “O Lord, the great and awesome God, who keeps his covenant of love with all who love him and obey his commands,” (Dan 9:4)
Any uncircumcised male, who has not been circumcised in the flesh, will be cut off from his people; he has broken my covenant. (Gen 17:14)
He replied, “I have been very zealous for the LORD God Almighty. The Israelites have rejected your covenant, broken down your altars, and put your prophets to death with the sword. I am the only one left, and now they are trying to kill me too.” (1 Ki 19:10)
The earth is defiled by its people; they have disobeyed the laws, violated the statutes and broken the everlasting covenant. (Isa 24:5)
They have returned to the sins of their forefathers, who refused to listen to my words. They have followed other gods to serve them. Both the house of Israel and the house of Judah have broken the covenant I made with their forefathers. (Jer 11:10)
“Therefore this is what the Sovereign LORD says: As surely as I live, I will bring down on his head my oath that he despised and my covenant that he broke.” (Ezek 17:19)
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