For Christians Who Doubt Their Salvation
As a Biblical Counselor, I counsel people wrestling with an assurance of faith regularly and I've wrestled with an assurance of faith in my own walk with the Lord before. A lack of assurance of faith can be the result of three things primarily:
First, it could be that you're not a believer and the Lord is convicting you of this. Praise God for this. The Holy Spirit is regenerating your heart of stone into a heart of flesh.
Or, it could be that you're living in habitual sin and the Holy Spirit has depressed you- it may seem as you are dried up on the inside. This is also good and the only response if your repentance.
There is a third reason why you may have a lack of assurance. We have an enemy- the 'accuser of the brethren' (Revelation 12:10). The accuser reminds you or your past sins, tempts you with the lust of your flesh, and whispers in your ear that your past sins and present temptations are your identity.
If you hear the voice of the accuser today, this article is for you my dear friend.
The Bible teaches and our Christian brothers and sisters all throughout church history have subscribed to a doctrine historically called the 'perseverance of the saints'. This doctrine teaches that no believer in Christ will ever fall from grace because God is both the author and the finisher of the faith (Hebrews 12:2).
"...he who has begun a good work in you will complete it until the day of Jesus Christ..." (Philippians 1:6b NKJV)
Charles Spurgeon, arguably the greatest preacher of the 19th century once stated, “I think few doctrines more vital than that of the perseverance of the saints, for if ever one child of God did perish, or if I knew it were possible that one could, I should conclude at once that I must, and I suppose each of you would do the same.” Elsewhere Spurgeon has stated, “If anybody could possibly convince me that final perseverance is not a truth of the Bible, I should never preach again, for I feel I should have nothing worth preaching.”
The Apostle Paul states in Ephesians 1:5, 13-14, “(5) He predestined us for adoption through Jesus Christ, according to the purpose of his will… (13-14) In him you also, when you heard the word of truth, the gospel of your salvation, and believed in him, were sealed with the promised Holy Spirit, who is the guarantee of our inheritance until we acquire possession of it, to the praise of his glory.” (italics mine)
God, in His perfect love (for He is love), elected us before the world was created based on His good character alone. This means that there is nothing in you or in me that influenced God's choice to save us. He saved us because He wanted to. Not only this but He accomplished our election through the death and resurrection of His Son, Jesus Christ. The only thing you and I contributed to Christ's sacrifice is our sin. He alone accomplished our election through His perfect person and work. The Holy Spirit then regenerated our hearts and we responded with repentance and faith. Furthermore the Holy Spirit (as the passage above states) is the “guarantee of our inheritance…”.
The Westminster Confession of Faith puts it this way: “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.” (17.1)
Not only is this doctrine comforting to those wrestling with assurance, but it is good and biblically sound to embrace. Hear me dear believer: Christ paid for all of your sins and every bit of God's wrath was satisfied on the cross.
The accuser's accusations come too late. Your past is not who you are. You are in Christ and “salvation belongs to the Lord” (Jonah 2:9).
Salvation is a gift from God- one He never takes back (Jeremiah 32:40; Romans 8:1; 2nd Timothy 4:18).
 Spurgeon, The New Park Street Pulpit, Vol. I, 233-234.
 Spurgeon, The Metropolitan Tabernacle Pulpit, Vol. VII, 223.