His personality would act as a paradigm for his descendants who would eventually become the Jewish people. He was a religious revolutionary who refined his spirituality to such a degree that G-d spoke to him, in other words, he became a Prophet (although his wife Sarah became a greater Prophet) He was an iconoclast who openly challenged the universal beliefs of his time and insisted that there was only one G-d. He was stubbornly willing to give up his own life rather than compromise his beliefs.
The people that would evolve from Abraham would have to manifest all of those qualities in order to perform the role that G-d had set for them. In fact the only time the Torah defines the nature of the Jewish people it is to identify them as a "Stiff necked" or stubborn. Still, if G-d required a people to carry a message through Crusade, Inquisition, Pogrom, and Holocaust, "stubbornness" would be the essential character trait.
Orthodox Judaism believes that the Jewish people left the slavery of Egypt and rendezvoused with G-d at a mountain called Sinai. There, through Moses, they would be given the Torah. Moses was also taught the deeper meaning of that book and that explanation was passed from teacher to pupil and was known as the 'oral tradition'.
The Torah's insistence of "An eye for an eye" for example, was never meant to be taken literally, Moses was taught that it meant the financial value of the lost eye. The Oral tradition was in fact a system which allowed the 304,805 letters that are contained in the Torah to expand into a set of legal rulings that covered, building law, agricultural law, criminal law, sexual Law, business law and in fact a complete set of legislation for every conceivable aspect of a society.
The form that the Talmud takes is a key set of statements know as the Mishna, which draws its information from the Torah. These statements are then discussed at great length sometimes comparing the information in one Mishna with another and clarifying seeming contradictions. Once the discussions reach a conclusion that becomes the Jewish legal ruling or Halachah. The Talmud also carries background to the stories in the Torah and so the dialogue in Genesis between Rachel and Jacob is expanded upon and a deeper insight gained.
After the destruction of the Temple in Jerusalem by the Romans in the year 70, the Talmud needed to be written down. Those who carried it in their minds were being systematically persecuted and killed by Rome. There was a danger that it could become lost and so the oral law too became written. Its' scope is vast and it is contained in twenty huge volumes as thick as a telephone directory and twice the height.
Evolving and Dynamic
Those unfamiliar with Orthodox Judaism, sometimes believe that it became fossilised some time in the past and is not an evolving and dynamic religion. This is certainly a myth.
The legal precedents and principles that were given at Mount Sinai are elastic and capable of expansion or contraction to meet any given situation. The range of the topics covered in the legal rulings of the great recent and contemporary authorities makes this quite clear. Rabbi Moses Feinstein (1895 -1986) was among the top three Jewish legal authorities in the world. His legal rulings range from In-vitro Fertilisation to advising the Surgeon General of America on surgical procedures. All his judgements are sourced in Halachah. The greatest current authority is Rabbi Eliashev of Jerusalem. The leading Jewish courts in the UK and throughout the world consult him. The scope of his decisions, demonstrate the ease with which the Halachah applies itself to contemporary issues.
The emergence of Rabbis with that degree of expertise and authority involves a process of intense study that spans many decades. Such Rabbis will be expected to have mastered the entire Talmud as well as all the later legal conclusions of people like Maimonides to present day authorities. They will have been rigorously tested, not just in their mastery of the Jewish Legal process, but their absorption of Judaism's highest ideals into their own personality and behaviour.