How do you know if you are a Christian? Scott Brown points out nine tests of salvation from the little, but significant, book of 1 John.
1. 1 John 1:5-7 (Walking in the Light)
5 This is the message which we have heard from Him and declare to you, that God is light and in Him is no darkness at all. 6 If we say that we have fellowship with Him, and walk in darkness, we lie and do not practice the truth. 7 But if we walk in the light as He is in the light, we have fellowship with one another, and the blood of Jesus Christ His Son cleanses us from all sin.
2. 1 John 1:8-10 (Confession of Sin)
8 If we say that we have no sin, we deceive ourselves, and the truth is not in us. 9 If we confess our sins, He is faithful and just to forgive us our sins and to cleanse us from all unrighteousness. 10 If we say that we have not sinned, we make Him a liar, and His word is not in us.
3. 1 John 2:3-4 (Obedience)
3 Now by this we know that we know Him, if we keep His commandments. 4 He who says, "I know Him," and does not keep His commandments, is a liar, and the truth is not in him.
4. 1 John 2:9-11 (Love for the Brethren)
9 He who says he is in the light, and hates his brother, is in darkness until now. 10 He who loves his brother abides in the light, and there is no cause for stumbling in him. 11 But he who hates his brother is in darkness and walks in darkness, and does not know where he is going, because the darkness has blinded his eyes.
5. 1 John 2:15-17 (Hatred for the World)
15 Do not love the world or the things in the world. If anyone loves the world, the love of the Father is not in him. 16 For all that is in the world--the lust of the flesh, the lust of the eyes, and the pride of life--is not of the Father but is of the world. 17 And the world is passing away, and the lust of it; but he who does the will of God abides forever
6. 1 John 2:24-25 (Perseverance in Doctrine)
24 Therefore let that abide in you which you heard from the beginning. If what you heard from the beginning abides in you, you also will abide in the Son and in the Father. 25 And this is the promise that He has promised us--eternal life.
7. 1 John 3:10 (Righteousness)
10 In this the children of God and the children of the devil are manifest: Whoever does not practice righteousness is not of God, nor is he who does not love his brother. 11 For this is the message that you heard from the beginning, that we should love one another,
8. 1 John 4:13 (Spirit's Testimony)
13 By this we know that we abide in Him, and He in us, because He has given us of His Spirit.
9. Hebrews 12:5-8 (Discipline)
5 And you have forgotten the exhortation which speaks to you as to sons: "My son, do not despise the chastening of the Lord, Nor be discouraged when you are rebuked by Him; 6 For whom the Lord loves He chastens, And scourges every son whom He receives." 7 If you endure chastening, God deals with you as with sons; for what son is there whom a father does not chasten? 8 But if you are without chastening, of which all have become partakers, then you are illegitimate and not sons
Here is a wonderful resource produced by Jeff Pollard in his Free Grace Broadcaster on Assurance
Paragraph 1 – How people deceive themeslves and how they are rightly assured
Although temporary believers, and other unregenerate men, may vainly deceive themselves with false hopes and carnal presumptions of being in the favor of God and state of salvation, which hope of theirs shall perish1; yet such as truly believe in the Lord Jesus, and love Him in sincerity, endeavoring to walk in all good conscience before Him, may in this life be certainly assured that they are in the state of grace, and may rejoice in the hope of the glory of God2, which hope shall never make them ashamed3.
Paragraph 2 –What is infallible assurance
This certainty is not a bare conjectural and probable persuasion grounded upon a fallible hope, but an infallible assurance of faith1, founded on the blood and righteousness of Christ revealed in the Gospel2; and also upon the inward evidence of those graces of the Spirit unto which promises are made3, and on the testimony of the Spirit of adoption, witnessing with our spirits that we are the children of God4; and, as a fruit thereof, keeping the heart both humble and holy5.
Paragraph 3 – How assurance is progressive and how you can make it grow
This infallible assurance doth not so belong to the essence of faith, but that a true believer may wait long, and conflict with many difficulties before he be partaker of it1; yet being enabled by the Spirit to know the things which are freely given him of God, he may, without extraordinary revelation, in the right use of means, attain thereunto2: and therefore it is the duty of every one to give all diligence to make his calling and election sure, that thereby his heart may be enlarged in peace and joy in the Holy Spirit, in love and thankfulness to God, and in strength and cheerfulness in the duties of obedience, the proper fruits of this assurance3;-so far is it from inclining men to looseness4.
Paragraph 4 – How your assurance can be shaken
True believers may have the assurance of their salvation divers ways shaken, diminished, and intermitted; as by negligence in preserving of it1, by falling into some special sin which woundeth the conscience and grieveth the Spirit2; by some sudden or vehement temptation3, by God's withdrawing the light of His countenance, and suffering even such as fear Him to walk in darkness and to have no light4, yet are they never destitute of the seed of God5 and life of faith6, that love of Christ and the brethren, that sincerity of heart and conscience of duty out of which, by the operation of the Spirit, this assurance may in due time be revived7, and by the which, in the meantime, they are preserved from utter despair8.