Romans 8:17

and if children, then heirs; heirs of God and join theirs with Christ; if so be that we suffer with Him, that we may be also glorified together.

Having pictured the blessed state of the Christians, the apostle now presents an admonition to them in the form of a conclusion: So, then, brethren, debtors we are. All Christians are under a very strong obligation on account of benefits and blessings received. But not to the flesh, to live in accordance with the flesh, as natural man is apt to believe that he owes his flesh the gratification of its desires, that he is obliged to live in accordance with its demands. By this figure of speech the apostle brings out very strongly the implication which he has in mind: We are debtors to the Spirit. For, he argues, if you Christians live in accordance with the flesh, following its dictates and inclinations, then the inevitable consequence, that which is bound to come upon you, is death. The mere fact that a person has embraced the truth in Christ at some time of his life will by no means make him safe for all times. If Christians permit their flesh, their old evil nature, to regain the ascendancy, to govern their life and actions, then there is only one result possible, eternal death. But if the Christians will at all times by the Spirit, through the power of the Holy Ghost in them, put to death the practices, the deceitful doings of the body, as an instrument of evil, then they will live, be preserved for eternal life: holiness, happiness, and everlasting bliss.

This fact, the certainty of the gift of eternal life through the mercy of God, if we remain on the way of righteousness and destroy the deeds of the body, is now proved: For as many as are led by the Spirit of God, these are the sons of God. Only those that have the Spirit of God are in truth members of Christ. And this Spirit moves, leads, urges the Christians on, all those under this constant and effectual influence of the Spirit being considered sons of God, being made sons of God, in fact, by the work of the Spirit. In and through Christ, whose redemption is imparted to them by the Spirit, they are brought into that intimate relation to God that He is their Father and they are His children by adoption, Galatians 3:26. And their state and relation of children is evidenced and proved by the fact that the Spirit is continually leading them in the way of righteousness. This relation to God is also a pleasant relation, one that invites and creates confidence: For not have you received the spirit of bondage again toward fear. Every man by nature leads a life of dread and fear, like that of a slave who fears the anger and punishment of his master. In a measure, the religion of the Old Testament was a religion which stimulated the spirit of bondage, according to which the Jews were always in dread and doubt as to their perfect keeping of the Law. But the Spirit which the believers have received is the Spirit of adoption, that of being made the children of God. The Holy Ghost brings about this relation of the believers toward God, He assures them with the confidence wrought by faith that God has adopted them as His children for the sake of Jesus, and in this confidence they cry out to Him: Abba, Father, the latter word being the translation of the Aramaic word which is in use to this day. It is an earnest cry, a vehement address, full of desire, trust, and faith. Thus the Spirit of God in us, in teaching us to trust in God with simple, childlike faith, gives us a certain, an indubitable witness, a definite proof and certainty, that we are the children of God. It is a conviction which is not found in our own spirit, which no man can have by his own reason and strength, which the Spirit of God alone can and does give. The very fact that this witnessing of the Spirit is entirely independent of our own feelings, of our state of mind at any given time, makes it so certain and reliable that we are dear children of our heavenly Father. But if children, then also heirs. If we are the children of God, then we are also sure of partaking of the inheritance of the saints in light; we are sure of the possession of the inheritance of Christ Himself, with whom we are joint-heirs by the fact of our adoption. As children of God we have a claim to the bliss of heaven, as God has prepared it for His only-begotten Son, for Him that was born out of the fullness of His divine essence. There is only one outward condition which is inevitable: If so be, if only we suffer with Him, in order that we may also be glorified with Him. Christians are partakers of the sufferings of Christ, they are bound to endure afflictions of many kinds for His name's sake. To attempt to evade these sufferings is equivalent to refusing to bear the cross of Christ, Mark 8:34; Luke 9:23. The bearing of the cross is not an absolute condition, but the inevitable lot of those that are awaiting the glory of eternal bliss, Galatians 4:7. And thus the beautiful, comforting doctrine of the adoption of the Christians as children of God, of their inheritance of eternal life, serves to admonish them to die unto the flesh and to live by the Spirit.