The Faithful are Promised the Spirit - Galatians 3:14

...receive the promise of the spirit through faith.

The blessing of Abraham is  priesthood, posterity, and prosperity. These blessings were made available to the gentiles through adoption by means of baptism. Then we receive the "promise of the Spirit" which is the gift of the Holy Ghost.

We read in v. 24:

Wherefore the law was our schoolmaster to bring us unto Christ, that we might be justified by faith.

This means that the law and commandments are there to point us unto Christ. But once we have entered into the faith (through baptism) the law and commandments in and of themselves do not justify us - it is only faith in Christ that does. Once we have received the Holy Ghost, it is our new schoolmaster - we are to follow His dictates. Thus the law is superseded by the Spirit. Faith relies on living revelation of the Spirit!