16Now the promises were made to Abraham and to his offspring. It does not say, “And to offsprings,” referring to many, but referring to one, “And to your offspring,” who is Christ. 17This is what I mean: the law, which came 430 years afterward, does not annul a covenant previously ratified by God, so as to make the promise void. 18For if the inheritance comes by the law, it no longer comes by promise; but God gave it to Abraham by a promise. 19Why then the law? It was added because of transgressions, until the offspring should come to whom the promise had been made, and it was put in place through angels by an intermediary. 20Now an intermediary implies more than one, but God is one.
The offspring has already been identified as Christ (verse 16). The Law was in force until Christ came. Christ abolished the Law. He abolished the whole Law.
For Christians to seek to live according to the Old Testament Law is to deny that Christ has fulfilled His purpose in coming to the earth. The Law was only put in place through angels and by an intermediary – Moses. The Gospel was put in place by God Himself and mediated by God the Son. It simply cannot stand up against what the Gospel can give.
Whatever Paul means by saying that the Law came through angels, the bigger point is that Jesus is better. Why see the Law as something glorious for the redemption of sinners when it is clear that the Gospel supercedes it in every possible way? This little phrase in Galatians 3:19 is expanded upon in detail in Hebrews chapters 1-3. Paul could, in these words about angels, be giving credence to the rabbinic belief that angels brought the Law to Moses. Even if that is true, Paul says, it pales in comparison to how we got the Gospel.
The teaching of Galatians addresses the undying tendency in us to find something in us that we do that makes God treat us favourably. Not many Christians will go to the Law of Moses and seek to keep it as a means of salvation. But we can and do draw attention to our gifts, our sacrifices, our service, our length of service … . We think that all these things make us more acceptable to God. That is a denial of the Gospel.
The human heart is an idol factory and we make ourselves look very good. We are wired to show cause why God should accept us. This is what will condemn us. No matter how spectacular our system, anything that adds to faith alone is heresy. If you have an answer other than the merits of Jesus Christ to the question “Why should God allow you into heaven?” then you have abandoned the Gospel.