For ye are all the children of God by faith in Christ Jesus. – Galatians 3:26

Faith is the mark of sonship in all who have it, whoever they may be, for ye are all the children of God by faith in Christ Jesus. If you are believing in Jesus, whether you are Jew or Gentile, bond or free, you are a son of God. If you have only believed in Christ of late and have but for the past few weeks been able to rest in His great salvation, yet, beloved, now are you a child of God. It is not an after privilege, granted to assurance or growth in grace; it is an early blessing, and belongs to him who has the smallest degree of faith, and is no more than a babe in grace. If a man be a believer in Jesus Christ his name is in the register-book of the great family above, “for ye are all the children of God by faith in Christ Jesus.” But if you have no faith, no matter what zeal, no matter what works, no matter what knowledge, no matter what pretensions to holiness you may possess, you are nothing, and your religion is vain. Without faith in Christ you are as sounding brass and a tinkling cymbal, for without faith it is impossible to please God. Faith then, wherever it is found, is the infallible token of a child of God, and its absence is fatal to the claim.

Henceforth you are one in Christ, you wear his name, you live in him, you are saved by him, you are altogether his. Now, if you are one with Christ, since he is a son, you are sons also. If you have put on Christ God seeth you not in yourself but in Christ, and that which belongeth unto Christ belongeth also unto you, for if you be Christ’s then are you Abraham’s seed and heirs according to the promise. ~ C.H. Spurgeon

https://www.blueletterbible.org/Comm/spurgeon_charles/sermons/1435.cfm

“The law was our schoolmaster to bring us unto Christ, that we might be justified by faith.” – Galatians 3:24

And because ye are sons… – Galatians 4:6

An unjustified man stands in the condition of a criminal, not of a child: his sin is laid to his charge, he is reckoned as unjust and unrighteous, as indeed he really is, and he is therefore a rebel against his king, and not a child enjoying his father’s love. But when faith realizes the cleansing power of the blood of atonement, and lays hold upon the righteousness of God in Christ Jesus, then the justified man becomes a son and a child. Justification and adoption always go together. “Whom He called them He also justified,” and the calling is a call to the Father’s house, and to a recognition of sonship. Believing brings forgiveness and justification through our Lord Jesus; it also brings adoption, for it is written, “But as many as received Him, to them gave He power to become the sons of God, even to them that believe on His name.”

“After that faith is come, we are no longer under a schoolmaster.” When we groaned under a sense of sin, and were shut up by it as in a prison, we feared that the law would punish us for our iniquity, and our life was made bitter with fear… but now that faith has come we see the law fulfilled in Christ, and ourselves justified and accepted in Him: this changes the slave into a child, and duty into choice. Now we delight in the law, and by the power of the Spirit we walk in holiness to the glory of God. Thus it is that by believing in Christ Jesus we escape from Moses, the taskmaster, and come to Jesus, the Saviour; we cease to regard God as an angry Judge and view Him as our loving Father. The system of merit and command, and punishment and fear, has given way to the rule of grace, gratitude, and love, and this new principle of government is one of the grand privileges of the children of God. ~ C.H. Spurgeon

https://www.blueletterbible.org/Comm/spurgeon_charles/sermons/1435.cfm

And because ye are sons… – Galatians 4:6

Adoption gives us the rights of children, regeneration gives us the nature of children: we are partakers of both of these, for we are sons. Let us here observe that this sonship is a gift of grace received by faith. We are not the sons of God by nature in the sense here meant. We are in a sense “the offspring God” by nature, but this is very different from the sonship here described, which is the peculiar privilege of those who are born again. The Jews claimed to be of the family of God, but as their privileges came to them by the way of their fleshly birth, they are likened to Ishmael, who was born after the flesh, but who was cast out as the son of the bondwoman, and compelled to give way to the son of the promise. We have a sonship which does not come to us by nature, for we are “born, not of blood, nor of the will of the flesh, nor of the will of man, but of God.” Our sonship comes by promise, by the operation of God as a special gift to a peculiar seed, set apart unto the Lord by His own sovereign grace, as Isaac was. This honour and privilege come to us, according to the connection of our text, by faith. Note well the twenty-sixth verse of the preceding chapter: “For ye are all the children of God by faith in Christ Jesus.” As unbelievers we know nothing of adoption. While we are under the law as self-righteous we know something of servitude, but we know nothing of sonship. It is only after that faith has come that we cease to be under the schoolmaster and rise out of our minority to take the privileges of the sons of God. ~ C.H. Spurgeon

https://www.blueletterbible.org/Comm/spurgeon_charles/sermons/1435.cfm