The question of exhorting one another should be commonly practiced everywhere we are in this world as Christians. Merriam-Webster defines: Exhortation is defined as the act or process of making a strong urging or appeal. An example of an exhortation is an emotional speech that inspires people to act.
So its strong. Urging someone. Appealing to someone. Emotional speech to inspire. That’s “exhort”. 12 Take care, brothers, lest there be in any of you an evil, unbelieving heart, leading you to fall away from the living God. 13 But exhort one another every day, as long as it is called “today,” that none of you may be hardened by the deceitfulness of sin.
The Reason of Exhortation
Because of the fear of falling away due to unbelieving hearts. Now it says “Take care, brothers…..less you fall..” (v12). This refers to believers, as brothers. So there is a possibility for believers born again Christians to fall away because of an evil unbelieving heart developed, obviously from believing heart in the first place. I guess this is backsliding to the scale of de-conversion like well written by Dr Michael Krueger on de-conversion. This should make us to be even more all out to exhort one another, because there is such a thing of de-conversion, the antithesis or opposite of conversion. It’s very sad, and there are few big names in America who have sided into that.
I know Westminster confession says, just like Calvin has said:
The Westminster Confession of Faith (19.1) states, “They whom God hath accepted in his Beloved, effectually called and sanctified by his Spirit, can neither totally nor finally fall away from the state of grace, but shall certainly persevere therein to the end, and be eternally saved.”
This is called the Doctrine of perseverance of the Saints. “The doctrine described says that the elect are not only redeemed by Christ and renewed by the Spirit, but that they are kept in faith by the almighty power of God.” That’s a very important phrase right there, “kept in faith” by the almighty power of God. We are not only saved redeemed by Christ and renewed by the Spirit, but KEPT in faith by God’s power. That means there is always a tug of war trying to pull us away from God by the forces in this world and the forces of devil.
Curtis Thomas puts it well, “This doctrine of the perseverance of the saints does not maintain that all who profess the Christian faith are certain of heaven. It is saints, those who are set apart by the Spirit, who persevere to the end. It is believers, those who are given true, living faith in Christ, who are secure and safe in Him. Many who profess to believe fall away, but they do not fall from grace, for they were never in grace. True believers do fall into temptation, and they do commit sins, but these sins do not cause them to lose their salvation nor do they separate them from Christ.”
The question is many who profess faith in Jesus also fall away, why? Because they were never in grace, therefore they can’t fall away from grace. But they so called profess their faith.
Where are the NT promises for that?
When we come to the New Testament (the new covenant) we find one promise after another that God will preserve His people. Jesus says, “it is not the will of my Father who is in heaven that one of these little ones should perish” (Matt. 18:14). In John chapter 6, Jesus promises, “All that the Father gives me will come to me, and whoever comes to me I will never cast out. … And this is the will of him who sent me, that I should lose nothing of all that he has given me, but raise it up at the last day” (John 6:37–39). Speaking of the Good Shepherd and the sheep, Jesus very clearly teaches the doctrine of the security of the believer: “My sheep hear my voice, and I know them and they follow me. I give them eternal life, and they will never perish, and no one will snatch them out of my hand. My Father, who has given them to me, is greater than all, and no one is able to snatch them out of the Father’s hand. I and the Father are one” (John 10:27–30).
Jesus said it “I shall lose nothing of all..”(v14).The “no one is able to snatch them out of the Fathers hand”. So those who fallen away, are those who were never in the grace.
Dr. Curt Daniel has done valuable work in explaining and setting these verses in their proper context in The History and Theology of Calvinism, Dallas: Scholarly Reprints, pp. 420–425. I conclude with his words: “The Reformed doctrine of perseverance is that a regenerate soul will certainly persevere through the trials of life and continue to believe and repent. He will slip and fall, develop bad habits, wrestle with doubts, but through it all he will keep on going even as he began. … all believers slip and fall into sin. But the truth of the matter is that no believer stays down. Just as God gave him faith and repentance unto initial conversion, so He supplies him with faith and repentance all along the way to heaven” (p. 415 ).
But the most important thing is “Do not harden your hearts…” for 40 years Israel tested God and saw the miracles of God for 40 years and yet there were a number of them who rebelled against God, fallen totally away. Imagine that? After seeing some of the phenomenal miracles that will pale anything we have seen today? So if they could fall away even after seeing greatest miracles one earth, watch out in your own lives. Don’t take things for granted. There must a continual fear of God, deep reverence of God and a sense of piety and love for him.
Hebrews 3:7-9 Therefore, as the Holy Spirit says, “Today, if you hear his voice, 8 do not harden your hearts as in the rebellion, on the day of testing in the wilderness,9 where your fathers put me to the test and saw my works for forty years.
Feeling God’s Anger & Frustration
10 Therefore I was provoked with that generation, and said, ‘They always go astray in their heart; they have not known my ways.’11 As I swore in my wrath,‘They shall not enter my rest.’”
Sometimes people forget that God has emotions too. He gets angry, and his holy anger rises and shown many times especially in the OT. He has deep passion for his people Israel in the OT, and in the NT and now, he has deep feelings for his church, who was purchased by his own blood. We are his. He is our God. Amen.
Hebrews 10:24 And let us consider how to stir up one another to love and good works, 25 not neglecting to meet together, as is the habit of some, but encouraging one another, and all the more as you see the Day drawing near.
 Curtis Thomas , Safe and Secure, https://www.ligonier.org/learn/articles/safe-and-secure/