3 Even so we, when we were children, were in bondage under the elements  of the world:
3 So also, when we were underage, we were in slavery under the elemental spiritual forces
3 In the same way we also, when we were children, were enslaved to the elementary principles
3 That is the way it is with us: When we were minors, we were just like slaves ordered around by simple instructions (the tutors and administrators of this world), with no say in the conduct of our own lives.
3 Even so we, when we were children, were in bondage under the elements of the world.
3 And that's the way it was with us before Christ came. We were like children; we were slaves to the basic spiritual principles of this world.
Matthew Henry's Commentary on Galatians 4:3
Commentary on Galatians 4:1-7
(Read Galatians 4:1-7)
The apostle deals plainly with those who urged the law of Moses together with the gospel of Christ, and endeavoured to bring believers under its bondage. They could not fully understand the meaning of the law as given by Moses. And as that was a dispensation of darkness, so of bondage; they were tied to many burdensome rites and observances, by which they were taught and kept subject like a child under tutors and governors. We learn the happier state of Christians under the gospel dispensation. From these verses see the wonders of Divine love and mercy; particularly of God the Father, in sending his Son into the world to redeem and save us; of the Son of God, in submitting so low, and suffering so much for us; and of the Holy Spirit, in condescending to dwell in the hearts of believers, for such gracious purposes. Also, the advantages Christians enjoy under the gospel. Although by nature children of wrath and disobedience, they become by grace children of love, and partake of the nature of the children of God; for he will have all his children resemble him. Among men the eldest son is heir; but all God's children shall have the inheritance of eldest sons. May the temper and conduct of sons ever show our adoption; and may the Holy Spirit witness with our spirits that we are children and heirs of God.