The law is good and spiritual, but it is weak. In its weakness, it is not able to give life (Gal. 3:21b). Regardless of how good, how holy, how righteous, and how spiritual the law is, the law cannot impart life to us. We sinners were not only evil but also dead (Eph. 2:1). The basic thing we need is life. The good law, the righteous law, the holy law, the spiritual law, is good, but it cannot impart life into us.
Furthermore, the law is not able to do that which God wants because it is weak through the flesh (Rom. 8:3a). The law itself may not be that weak, but the law is given to the flesh, and the flesh is the law's companion. The law is not that weak, but its companion, the flesh, is weak to the uttermost. We need to consider how weak we are. Many of the sisters are easily offended. If you offend them, they will not forget it. To remember another person's faults is not good. The Bible tells us that forgiving means forgetting (Heb. 8:12). As long as we still remember another's fault, this indicates that we have not forgiven him. The proper forgiving is to forget. Forgiving and forgetting seem to be a small thing, but we cannot fully overcome in this matter. This shows that we are weak. Because we are weak, we are the instrument to the law, so the law becomes weak.
Out of the works of the law no flesh will be justified before God (Rom. 3:20a; Gal. 3:11a). This is repeated by Paul in both Romans and Galatians.
The law was the center and requirement of the old covenant. The law was for the old covenant in God's economy.
The law, as the requirement of the old covenant, is to be performed by men's work (Gal. 3:12b). The law has to be performed. Without man's performance, the law means nothing.