What is assurance of salvation according to the Bible?

“These things have I written to you that ye may know that ye have eternal life, who believe on the Name of the Son of God” (JND). It may easily be the case that one may have eternal life, and yet not know it. For this very reason John has written. Not that this is the only reason, for other definite reasons are also mentioned in ch.1:3; 1:4; 2:1. The Father desires none of His children in doubt as to the precious reality of their possessing now the matchless gift of eternal life. Apart from the Word of God we could never have this assurance: it is a Divine revelation, not by means of personal introspection, feelings, or experiences, but by the written Word. This alone gives certainty. If one truly believes in the Name of the Son of God, he has eternal life, whether he realizes it or not. Scripture says so; and by Scripture alone can he realize it, and be absolutely assured. What matchless grace then that God has given us His Word!

The apostle presses this. Much that he had written before might be misused to lead sincere souls to look to themselves, their experience and their walk, for full assurance of having eternal life. Surely the fruits of life are to be theirs, as well as the life itself. Hence such passages as 1 John 2:5-29, 1 John 3:7-14, 18, 19, 24, 1 John 5:4. But he would not close the Epistle without making the clearest statement that the one sure ground of assurance is faith in God's testimony, not making light of the comfort flowing from other assurances. "These things have I written unto you that ye may know that ye have eternal life, (even) you that believe on the name of the Son of God." And remark, that here the verb "know" means conscious knowledge (chap. 5:13, R.V.). Divinely assured of the possession of eternal life, our thoughts are led to that which is proper to it — confidence in God (1 John 5:14). This is remarkably beautiful, because *blessedly practical. We are still in the body, still in the world where we have tribulation (John 16:33); but the relationship of children to God is known, and is proper to eternal life (John 17:3). The Spirit of His Son in our hearts cries, "Abba, Father" (Gal. 4:6), and our very groanings are heard (Rom. 8:26-27); so that in the depths, as to circumstances, we have all the resources of God. When we think of all He has done for us, how can we limit Him? He has a delight in our prayers (Prov. 15:8), and would secure to us exceeding quietness and rest of spirit, whatever the turmoil and distractions around us.

What is it to have eternal life? It is to have Christ. "He that hath the Son hath life." "This is the record, that God hath given to us eternal life, and this life is in His Son." Observe, it is the gift of God, and it is "in His Son." It is not in our keeping, but is secured for us in Christ. (1 John 5:12.) So we read, "When Christ, who is our life, shall appear." (Col. 3:4.) Faith believes the record of God, receives Christ, and passes from death unto life; as JESUS says, "He that heareth My word, and believeth on Him that sent Me, hath everlasting life, and shall not come into condemnation" [judgment, it should be], "but is passed from death unto life." (John 5:24.) How simple! May it be yours, dear reader, if not sure of your portion in Christ, to receive what God gives in the simplicity of faith. He has given His word for the purpose of removing every difficulty. "These things have I written unto you that believe on the name of the Son of God, that ye may know that ye have eternal life." (1 John 5:13.)

Verse 13. "These things have I written unto you that believe on the name of the Son of God, that ye may know that ye have eternal life." I am not writing to you, says John, to bring you the blessings of the testimony of God, as though you were not in possession of them, but to remind you that you have them, in order that you may be forearmed against the false teachers when they call your privileges in question.

On this therefore the apostle reasons and appeals in 10-12. It is God's testimony about His Son; and he that believes on Him has the testimony in himself, if all else failed; for the life is in Him for security and association with Him, as we have it really for present exercise and fellowship every day. "He that hath the Son hath life; he that hath not the Son of God hath not life." Very weighty is the sum here: "These things wrote (or, write, ep. aor.) I to you that ye may know (εἰδ) that ye have life eternal, ye that believe on the name of the Son of God." It is conscious knowledge.

We have now to consider what is said concerning the Spirit as dwelling in us. We are sons, and by the Spirit cry, "Abba, Father," in the consciousness of being so. The Holy Ghost Himself (here we have Him definitely as a distinct Person) "beareth witness with our spirit that we are the children of God." It is a distinct definite testimony of the Spirit who dwells in us that we are such; not a proving by the word on examination of ourselves (a false and unscriptural and evil procedure), but the testimony of the Holy Ghost Himself dwelling in us, which He bears to us as so dwelling in us. We have the consciousness and estate of the mind of the Spirit in us; but He Himself, as dwelling in us, bears consciously also to us the witness that we are sons. We are in the conscious relationship, but He who is in us gives the confidence-producing testimony.

But here we speak rather of the Spirit as dwelling in God's children, and as such, as we have seen, He "bears witness with our spirit, that we are the children of God" (Rom. 8:15-16; Gal. 4:6-7). In this aspect, He is the witness of accomplished redemption to the individual soul — as will be seen when treating the next point — and hence every child of God ought to know by this sure testimony that he is saved. But it may be asked, How is this witness borne to our sonship? The very fact of His presence within us testifies to it; but by His presence He forms within us affections suited to our relationship, begets in us desires after the enjoyment of the Father's love, enables us in the holy intimacies of our filial place and position to cry, Abba, Father, verifies to our souls the word on which we have trusted as revealing to us the relationship and the blessings which belong to us as God's children, and thus bears very distinct witness with our spirit. No! it is not an audible testimony, and it is discerned and apprehended by our spirit alone; but it is none the less, nay, it is all the more, real on this account, because indeed it is a living secret between ourselves and God. The strength and distinctness of His testimony, it ought not to be forgotten, will depend upon conditions. "As many as are led by the Spirit of God, they are the sons of God." In other words, just as being led by the Spirit of God is an evidence of our being the sons of God, so it is, when we are led walking in simple, loving obedience and dependence, that our spirit will discern most clearly His testimony to our sonship. But if we are so walking as to grieve Him, we shall listen in vain for His testimony, for we shall have grieved Him into silence. God will not therefore permit any of His children to walk carelessly, resting the certainty of their salvation on the ground of their being children; but He reminds us that if we are His we shall be led of the Spirit, and that He will bear witness with our spirit, and teach us to cry, Abba, Father.

There is, however, another thing. The apostle proceeds, "The Spirit itself beareth witness with our spirit, that we are the children of God." (Rom. 8:16.) The possibility of all self-deception is thus obviated. There might be the imitation of others in calling God Father, but there is also produced by the Spirit the inward consciousness of the relationship. It is important to remark that it does not say, bear witness to our spirit. If this were the language employed, we might be waiting for some distinct testimony at a given moment to assure us that we were now God's children. The apostle says, "with our spirit;" i.e., the fruit of the indwelling Spirit is to beget in us feelings and affections suited to, and to lead us into the enjoyment of, the relationship into which we are brought. The child of God now knows the Father, and does not doubt that he is a child, for he has within himself the assured consciousness of his relationship, and is able therefore to repose, in measure at least, in the enjoyment of the Father's love and care. In other words, the filial spirit is the product of this testimony of the Holy Ghost.

Rom. 8:16. "The Spirit itself beareth witness with our spirit, that we are the children of God." This passage, which, in experience leaves no difficulty, presents one when it is a question of saying what it means. If I separate from my spirit the witness of the Spirit of God, I leave no witness at all. If I receive the witness of the Spirit, then I have two; I have the certainty in my own spirit that I am a child of God, and I have besides the witness of that Spirit which works in us as the Spirit of adoption. It is the Spirit of God in us who gives to our spirit the strength to say that we are children of God.

So also in verse 16 He bears witness with our spirit that we are children of God. To understand this well we must remember that all saints from Adam downward have been children of God, though until the cross of Christ they did not have the position of sons of God. The Greek words in v. 14 and v. 16 are distinctly different — the latter implying birth, the former referring to the dignity of position as adopted. But while, as we have said, even Old Testament saints were children (not sons) of God, yet they had not the same confirming witness of this that we have today. There was not the same proof of it enjoyed in their souls: they were yet infants (Gal. 4:1), truly born again of God, but little conscious of the blessedness of their relationship. But the gift of the Spirit is a witness to us — within us — bearing witness with our spirit that we are children of God. This is a witness that Old Testament saints did not have. We today enjoy the relationship of children in the same measure in which we pay attention to the witness of the Spirit. The Spirit of course draws our affections out to Christ and gives us to delight in the things of God — the more so the more fully we allow Him His place. The fact also that we are sons of God by adoption, in virtue of redemption, is in itself proof that we are “children of God.” Adoption and new birth are distinct truths, of course, teaching most precious lines of thought, but there is no adoption without new birth, and since the cross of Christ every new-born soul has also received the adoption. New birth speaks of filial relationship: adoption speaks of positional dignity.