The Law, given to Moses on Mt. Sinai, was God's second work intended to make A People for Himself. The first work we know as God's creating man in His image, according to His likeness, in which thus the Word of God was in his heart as it was certainly of God's own heart. For Moses writes in Deuteronomy 30:14,
But the word is very near you, in your mouth, and in your heart, that you may do it.
Following man's fall in the Garden and the subsequent corrupting of that heart first created in man, there came in time the need for an objective Word that existed beyond the corrupting influences of man's heart. Not necessarily a new Word but more His first Word written anew. And it was a relatively unknown people, descendants of God's friend Abraham, through whom God intended once again to make for Himself A People. From the divine perspective of God, His intents and purposes were and always had been for the world at large, not for just a particular people themselves. As such, the Jews as a body coming up from the land of Egypt were then God's chosen and beloved instrument, in keeping with His promises to Abraham and Isaac and Jacob, for bringing the knowledge and presence of God as well as now His written Word to the world, A People through whom also later this Word, made flesh, would come, blessed to the world for its salvation and eternal life in Him.
So then, for every believer in the Risen Lord Jesus Christ, the question is not whether Jews, or Gentiles,--of which as Scripture declares there is but one believer and he or she neither Jew nor Greek--are yet commanded to "keep the Law". The question is rather why any believer would not want to keep the Law, being as it is the right and true Word of Holy God and being as it was given to the world only but through a particular people, His beloved Jews? There were two primary purposes, for the Jew first, and then also for the Gentiles, for the Teachings, or Law, of Holy God: the first for salvation the second for a way of life and living (not according to culture but according to the Spirit). Christ indeed fulfilled the horrific aspect of the Law's inability to save, its being able only to condemn, and through Christ, by faith alone and by His having perfectly fulfilled the Law, we have the promise of eternal life in Him. But as to the second intent of the Teachings, Christ did not come to destroy or annul these Teachings, and declared that anyone who does so destroy or annul even the least of these Teachings will be called least in the Kingdom of Heaven. Rather, the Teachings of God are still very much in force today for life and living before God and the world. Again, not for salvation, but for how to live and conduct ourselves in our walk before God and the world.
So, again, why would a believer in Christ indeed not want to follow, no matter by whom or in what manner His Teachings have come down to the world today, as many of the Teachings of God as possible which He blessed to us through His Word? Ought each of us not rather sit down now and take up the Holy Scriptures and, beginning with Genesis 1:1 and ending with Revelation 22:21, begin writing out God's Teachings for how we are to live, what feasts we are to observe, what commands we are to keep, especially irrespective of most if not all the cultural dictates of man, to the Glory and Honor of His Holy Name alone?