Jane Eyre was that stalwart of Victorian fiction - a governess. She had control over the children of the household. No doubt the oldest son would one day inherit the whole pile, but while he was under her tutelage her word was law. He might be master one day, but for today she was mistress. Her position was like that of the pedagogue of Galatians 4:2; a servant yet still in control of the heir or in Roman times - a slave. Paul is telling us that the law is like a governess Galatians 3:24 put in charge of us until we reach maturity.
In verse 19 Paul asks rhetorically, "What then is the purpose of the Law?" The first answer he gives is because of sin. in Romans 4:15 he writes that where there is no law there is no transgression. It is the Law that holds up a magnifying glass to sin. Look at a beige carpet. It looks fine; no blemishes. But examine it with a magnifying glass, Sherlock, and you will see the stain where last week you spilled the tea, the slight dab of tomato ketchup when you ate your supper on your knee because you were too lazy to lay the table; the speck of mud when you didn't wipe your boots properly and the posit of vomit from when your baby granddaughter visited.
I didn't know what coveting meant until I read the ten commandments. I certainly didn't know it was wrong. If that were not enough, the Sermon on the Mount is like an electron microscope on sin. It magnifies ten thousand times! It's not just murder or adultery but the attitude of the heart that counts.
The second reason that Paul gives is that the Law is temporary. It was added until the Seed that was promised had come. In other words it lasted until Jesus, the Messiah, came.
My wife had her wisdom teeth out when she was 20. Still her father had to sign the consent form. In those days you had to be 21 to be an adult. Today in the UK we have something called Gillick competence. It arose because Mrs Gillick thought that 14 was too young for her daughter to be on the pill. Learned judges decided that young girls could decide that at an early age. Seems to me that it gives a license for pedophiles, but the age of maturity has been known to be different for different things; 14, 16, 18, 21? Paul marks the age of maturity with an event; the coming of the Messiah. Things are different now; the Law is written in our hearts.
There is a mistranslation in verse 24. Both the KJV and older editions of the NIV have it wrong. The Law was not put in charge to lead us to Christ. There is no way that the Greek can be so translated. The marginal note in the older NIV has been incorporated in the text of newer edition. The law was put in charge until Christ came.
There is also a difference between the old agreement and the new. The Old Covenant was conditional; God would do this, if Israel did that. It is said that there were two tablets of stone the way that we have two copies of a contract; one for each party. The New Covenant is unconditional. It depends on one party only (verse 20). God promises this. There is no promise on our behalf. If we sin we are not condemned. If we sin we are forgiven. Amazing but true. How can it be? Because our sin was already punished on the tree. We may be rubbing salt in the wounds of the Savior, but nevertheless we are forgiven.
Paul asks a second question, "Is the law opposed to the promises of God?" The answer is a definite 'No'. Absolutely not!. If the law could have imparted life it would certainly have done so. It was pointing in the right direction. But it had no power to do so (verse 21). It fizzled out. Instead what was promised, given through faith in Jesus Christ, is life, and eternal life at that (verse 22). The law was like a prison. We were held fast by its precepts. Imagine a man sitting on a chair, his arms on the armrests. Here is a simple phrase of the law and ... SNAP! a manacle clamps down on his wrist. Another word from Leviticus and his other wrist is made fast. Here is an undiscovered clause from Deuteronomy and his feet are fettered. If thou should mark our iniquities. who could stand? The whole head is sick and the whole heart is faint. From the sole of the foot even to the head, there is no soundness in it, but bruises and sores and raw wounds. The heart is deceitful above all things and exceedingly corrupt; who can know it. The Law is all diagnosis and no treatment.
We were in prison then ... My chains fell off! I was free!
Now that faith has come, we are no longer under the supervision of the law (verse 25).