Galatians 3:24

"So that the law hath been (that is, hath turned out to be) our schoolmaster (or "tutor," literally, "pedagogue": this term, among the Greeks, meant a faithful servant entrusted with the care of the boy from childhood to puberty, to keep him from evil, physical and moral, and accompany him to his amusements and studies) to guide us unto Christ," with whom we are no longer "shut up" in bondage, but are freemen. "Children" (literally, infants) need such tutoring (Gal 4:3). might be--rather, "that we may be justified by faith"; which we could not be till Christ, the object of faith, had come. Meanwhile the law, by outwardly checking the sinful propensity which was constantly giving fresh proof of its refractoriness--as thus the consciousness of the power of the sinful principle became more vivid, and hence the sense of need both of forgiveness of sin and freedom from its bondage was awakened--the law became a "schoolmaster to guide us unto Christ" [NEANDER]. The moral law shows us what we ought to do, and so we learn our inability to do it. In the ceremonial law we seek, by animal sacrifices, to answer for our not having done it, but find dead victims no satisfaction for the sins of living men, and that outward purifying will not cleanse the soul; and that therefore we need an infinitely better Sacrifice, the antitype of all the legal sacrifices.

— Jamieson-Fausset-Brown Commentary (public domain)