The Spirit of Sonship: Killing Sin and Crying Abba Text: Romans 8:12-17
Introduction: Slaves or Sons?
The modern evangelical world is afflicted with a peculiar kind of spiritual amnesia. We have rightly emphasized the glorious truth that we are saved by grace through faith, and not by works. But in our flight from the ditch of legalism, many have tumbled headlong into the opposite ditch of antinomianism, which is just legalism's lazy cousin. We have taken the glorious liberty of the sons of God and mistaken it for a permission slip to live like spiritual layabouts. We think of salvation as a one-time transaction that gets our fire insurance paid up, and now we are free to do as we please. But the Apostle Paul will have none of this.
Having brought us through the glorious courtroom drama of justification in the early chapters of Romans, and having declared that there is now no condemnation for those who are in Christ Jesus, he does not then say, "So relax." No, he says, "So then, brothers, we are under obligation." The Christian life is not the cancellation of all debts; it is the transfer of our debt. We have been bought with a price. We are no longer indebted to our old slave master, the flesh, but we are now joyfully and eternally indebted to the one who freed us. We are under a new obligation, a new command, and a new power.
This passage before us is the very heart of practical Christian living. It lays out the two paths that are before every man: the path of the flesh that leads to death, and the path of the Spirit that leads to life. And it defines the Christian not as someone who has merely prayed a prayer, but as one who is actively engaged in a Spirit-powered war against sin, and who lives in the glorious new reality of being an adopted son of the living God. This is not about trying harder. This is about a fundamental change of identity, from a slave cowering in fear to a son crying out in love to his Father.
The Text
So then, brothers, we are under obligation, not to the flesh, to live according to the flesh, for if you are living according to the flesh, you must die, but if by the Spirit you are putting to death the practices of the body, you will live. For as many as are being led by the Spirit of God, these are sons of God. For you have not received a spirit of slavery leading to fear again, but you have received the Spirit of adoption as sons by whom we cry out, “Abba! Father!” The Spirit Himself testifies with our spirit that we are children of God, and if children, also heirs, heirs of God and fellow heirs with Christ, if indeed we suffer with Him so that we may also be glorified with Him.
(Romans 8:12-17 LSB)
The Great Obligation (v. 12)
Paul begins with a logical conclusion from everything he has just said about the Spirit giving life.
"So then, brothers, we are under obligation, not to the flesh, to live according to the flesh, " (Romans 8:12 LSB)
Grace does not abolish duty; it establishes it on a completely new footing. We are debtors. But to whom? Paul's great point here is a negative one. We are debtors, but emphatically not to the flesh. The "flesh" here is not our physical body, but our fallen, unregenerate human nature, oriented away from God and toward self. It is the principle of rebellion that we inherited from Adam. And Paul says we owe it nothing. We owe it no allegiance, no obedience, no deference. Why? Because it is a defeated tyrant. Christ broke its power at the cross. To go on serving the flesh after you have been set free by Christ is like an emancipated slave deciding to go back to the plantation to pick cotton for free. It is utter insanity.
Our old master, the flesh, promised pleasure and freedom but only ever paid out in addiction and death. We have been liberated from that fraudulent contract. Our obligation has been transferred. We are now under a joyful obligation to God, who has given us His Spirit. This is the obligation of love, the kind a grateful son owes to a gracious father, not the kind a terrified slave owes a cruel master.
The War and the Weapon (v. 13)
Verse 13 lays out the stakes of this new obligation. There are only two ways to live, and they have two very different destinations.
"for if you are living according to the flesh, you must die, but if by the Spirit you are putting to death the practices of the body, you will live." (Romans 8:13 LSB)
First, the stark warning. "If you are living according to the flesh, you must die." This is not complicated. A life that is characterized by the flesh, a life that makes peace with sin, a life that is not at war with its own corruption, is a life that is spiritually dead and headed for eternal death. Paul is not saying that true Christians can lose their salvation. He is saying that a life dominated by the flesh is proof that there was no spiritual life there to begin with. The fruit reveals the root. If the direction of your life is consistently toward the flesh, you are on the road to perdition, regardless of what prayer you once prayed.
But then comes the glorious alternative. "But if by the Spirit you are putting to death the practices of the body, you will live." This is the central activity of the Christian life. It is called mortification, which is just a King James word for "putting to death." Notice the mechanics of this. You are the one doing it. It is an active, violent, ongoing command. You must kill your sin. But you do not do it in your own strength. You do it "by the Spirit." This is the divine synergy. We are not passive. We fight, we strive, we kill. But the power to do so, the weapon in our hands, is the Holy Spirit Himself. This is not grim, joyless legalism. This is Spirit-empowered warfare. And the result is life, true, abundant, and everlasting life.
The Mark of a True Son (v. 14)
How can you know if you are a child of God? Paul gives us the definitive, observable evidence in verse 14.
"For as many as are being led by the Spirit of God, these are sons of God." (Genesis 1:3 LSB)
The defining mark of a Christian is not a past experience but a present reality. Are you being led by the Spirit? This leading is not some vague, mystical nudge or a goosebump in a worship service. To be led by the Spirit is to be guided, governed, and directed by Him in accordance with the Word of God. The same Spirit who inspired the Scriptures now lives in us to incline our hearts to obey them. The Spirit leads us to prayer. He leads us to repentance. He leads us into the battle of mortification we just read about. If the Spirit is leading you into a war against your own sin, then you have the unmistakable evidence that you are a true son of God.
Notice the glorious title: "sons of God." This is a position of immense privilege. In the ancient world, a son was the heir, the one who shared the father's honor and authority. This is what God has made us in Christ.
From Slavery to Sonship (v. 15-17)
In these final verses, Paul unpacks the magnificent reality of what it means to be a son.
"For you have not received a spirit of slavery leading to fear again, but you have received the Spirit of adoption as sons by whom we cry out, 'Abba! Father!'" (Romans 8:15 LSB)
The life you lived under the flesh was a life of slavery. Your master was sin, and your motivation was fear. Fear of punishment, fear of exposure, fear of God's wrath. This is the default religion of mankind. But that is not what you received when you came to Christ. You received the "Spirit of adoption." Adoption is a legal act. God the Father has gone to the cosmic slave market of sin, purchased you out of bondage, brought you into His own family, and legally declared you to be His son, with all the rights and privileges that belong to His only begotten Son, Jesus Christ.
And the immediate result of this adoption is a radical change in our relationship with God. We no longer cower before Him as a slave before a master. Instead, we cry out, "Abba! Father!" Abba is the Aramaic word for Father, a term of intimate, affectionate trust. It is what a small child would call his father. It is how Jesus Himself prayed in the Garden of Gethsemane. The Spirit in us moves us to address the sovereign God of the universe with the same intimacy and confidence that Jesus has.
This is not just a feeling; it is a confirmed reality.
"The Spirit Himself testifies with our spirit that we are children of God, and if children, also heirs, heirs of God and fellow heirs with Christ, if indeed we suffer with Him so that we may also be glorified with Him." (Romans 8:16-17 LSB)
Our assurance is not based on our own fickle emotions. It is based on a double testimony. The Holy Spirit Himself bears witness to our spirit, confirming from the outside in that we belong to God. And our own spirit, having been made alive, responds to this witness and cries out "Abba," confirming from the inside out that we are His children. This is a settled, objective fact that produces a subjective, joyful confidence.
And the logic of this reality is staggering. "If children, also heirs." Sonship means inheritance. And what is the inheritance? It is not a mansion over the hilltop. We are "heirs of God." We inherit God Himself. And we are "fellow heirs with Christ." Everything that belongs to the Son is now shared with us. We are destined to share in His glory, to rule and reign with Him over the new heavens and the new earth.
But this glorious inheritance comes with a condition, a path that must be walked. We are glorified with Him if we suffer with Him. This is not a suggestion that we might lose the inheritance. It is a description of the road that leads to it. The path to the crown is always by way of the cross. This suffering is the conflict that comes from being loyal to Christ in a hostile world. It is the pain of mortifying sin. It is the reproach we bear for His name. This suffering is not a sign that God has abandoned us; it is the family trait, the proof of our adoption, and the sure prelude to our coming glory.