This passage is about the Law. When read in the paraphrase The Message it becomes clear how God in His love for us made a way for us to be with Him (which we celebrate during Advent). Paul explains that God made a promise to Abraham that He would send a Savior. Then, the law came. Paul explains that the presence of the Law does not negate God’s promise. The law, rather, is like a flashlight or a light which one uses to illuminate a dark room only to see that it’s a mess in there.
Paul says the Law shows us how futile it is to devise a system whereby by our own efforts we achieve a godly life (v. 21). He explains how only faith in Christ saves, not faith in anything else we cling to. If we could keep rules and thereby achieve what God wants, it would have happened by now, Paul says. Makes sense to me. I can see Paul’s point by reading the headlines in the daily paper. I can also see Paul’s point when I look at my life. I do fine about as long as I’m sitting in my chair with my Bible. Me trying to live real life in a godly manner is another matter. I can’t do it by a system of trying to obey rules.
The part of this passage which comforts me, then, is when Paul discusses faith. God kept His promise and I thank Him, as I celebrate Christmas.