The physical descendants of Abraham and Sarah’s union were intended to be the “holy nation” that God called to be His priesthood for the world. They would learn the ways of Yahweh and thus be equipped to enlighten other nations. His exclusive covenant with Israel had been as follows:
So now, if you are really prepared to obey me and keep my covenant, you (Israelites) out of all peoples shall be my personal possession, for the whole world is mine. For Me you shall be a kingdom of priests, a holy nation. (Ex19:5,6)
So in due course He gave them the Decalogue along with more detailed requirements concerning how they were to conduct themselves, set out in the Torah of Moses or Pentateuch which scripture generally refers to as “the Law”. It was to be their schoolmaster up until Christ, for contrary to the teaching of many, justification by faith in a Saviour was not disclosed even to God’s chosen people before His coming, as a careful reading of Gal3:23-27 (Greek interlinear) affirms. When Paul asserts in that passage that justification on the basis of the faithfulness of Christ for those who had exercised faith had “not yet been disclosed” (v23 Greek) he was not saying it had not availed for those Jews who had been faithful, but their instruction had always been to “keep Torah” not to “acknowledge their moral impotence and trust in God’s mercy or the merits of a coming Saviour” or suchlike as Augustine and later the Reformers asserted.
At the same time, Paul was making it clear that no one had ever been justified on the basis of a perfect fulfilment of the Law (v21); it had always been on the basis of Christ’s faithfulness availing for those with “faith”. Yet once that was disclosed, the Torah as schoolmaster would be filled out by the teaching of Christ, and with the enabling that would be provided through an interior participation with Him and the Spirit, the children of God would come to obey what James referred to as the “royal law” of love for God and neighbour (cf. Jam2:8) and would do so “in spirit and in truth” rather than the deadness of the letter. In the meantime it is quite clear from the above quote from Exodus that the chosen nation were to be obedient to their covenant with Yahweh if they were to occupy a land that He had promised to Abraham. The occupants to be displaced were the polluted seed pool of Canaan, the accursed son of Ham that we considered earlier. Their supplanters were to become a divinely disciplined and holy nation to act as a salvific bridgehead to the rest of creation (Dt4:5,6). It had never been intended that the whole world “become Jewish” but neither was it destined for the cosmic waste-paper basket; many in the world would be enlightened by the Jews and come to revere Yahweh.
How the above assertions are squared with the teaching of the New Testament is set out in the Fellowship of the Secret – available freely as a PDF from HERE