The sages who taught the teachings, ordinances and decrees which make up the Talmud represented the totality of the sages of Israel, or at least the majority of them. Because of this, and because the Talmud was accepted as binding by almost the entire Jewish people at the time, its laws are considered binding on all Jews no matter when or where they live. 28 And it is precisely this binding that has kept our Jewish identity strong for thousands of years throughout this long and bitter exile. May we merit the ultimate redemption speedily in our days!
However, Jacob Neusner argues that the Mishnah does far more than expound upon and organize the Biblical commandments. Rather, important topics covered by the Mishnah "rest on no scriptural foundations whatsoever," such as portions of the civil law tractates of Bava Kamma , Bava Metzia and Bava Batra .  In other words, "To perfect the [Written] Torah, the Oral tradition had to provide for a variety of transactions left without any law at all in Scripture."  Just as portions of the Torah reflect (according to the documentary hypothesis ) the agenda of the Levite priesthood in centralizing worship in the Temple in Jerusalem and legitimizing their exclusive authority over the sacrificial cult, so too can the Mishnah be seen as reflecting the unique "program" of the Tannaim and their successors to develop an egalitarian form of Judaism with an emphasis on social justice and an applicability throughout the Jewish diaspora.   As a result, the Talmud often finds the rabbis combing scripture for textual support to justify existing religious practice, rather than deriving the practice organically from the language of scripture. 
The Yahwist was especially interested in those traditions that supported the legitimacy of Davidic rule and the centrality of the tribe of Judah. He (or she, if Bloom, 1990 is correct) believed that Gods plan was working itself out in the rule of David and Solomon. The Yahwist came from Judah, so understandably thought highly of King David. David was originally from Bethlehem in Judah, and first ruled from Hebron, an influential city in Judah, for many years. The Judah connection is evident in the Yahwists interest in Abraham. The bulk of the Abraham traditions are associated with locations in and around Judah. For example, several Yahwist stories of Abraham have him living in Hebron (Genesis 13:18; 23:2). On the other hand, the Jacob stories are generally located in the north or in Transjordan.