Our textbook indicates some of the difficulties in defining Judaism as a religion. This specifically has to do with the fact that there are those who consider themselves Jewish but not for religions reasons. Because of this the book discusses religious Judaism.
The book brings out distinctives of Judaism: its focus on God the creator, that God acts in history for redemptive purposes, and that God has given a law by which humans are to live to understand his purpose.
The acts of God in history are recorded in scripture, or special revelation. For Judaism these include the 5 books of Moses, the histories, the wisdom literature, and the prophets (all of which Christians refer to as the Old Testament). After the creation account (which includes creation, fall, and redemption), and then two accounts of humanity going into apostasy (the Flood and the Tower of Babel), the book of Genesis focuses on Abraham and his descendants as the chosen people by which God will reveal redemption for humanity.
The book tells us about the promises made to Abraham. These are given in connection with something he is to leave. In leaving the city of Ur, he will be given a promised land. In leaving his people he will be made the father of a great nation. And in leaving his father's family all nations will be blessed.
This blessing is in connection with Ur and that nation not being blessed. In their idolatry these people did not know God. They had gone astray. By way of contrast, through the work that God would do in Abraham and his descendants all people will come to know God.
The way that people come to know God is by keeping his law. At Mount Sinai this law was initially revealed in the ten commandments, which are elsewhere said to be written on men's hearts. That is, these are moral laws that all men can know, but which are summarized in the ten commandments. These commandments are then applied to all other areas of life.
While the book focuses on the law, what is central to Biblical Judaism, and what makes it distinct from other religions, is the role of the atoning sacrifice. While polytheistic groups offer sacrifices, these are given to placate the gods or to win their favor. By contrast, in Biblical Judaism there is a sacrifice to atone for the sins of the people. In this ceremony, the animal stands in the place of the one needing redemption and suffers the consequences of sin.
This was especially brought out in the life of Abraham in the act of offering his son Isaac. God told Abraham to offer Isaac, which could be a puzzling command for any parent. As he and Isaac proceeding to the place for the offering, Isaac asked Abraham where was the animal for the offering. Abraham replied that God would provide the sacrifice. Abraham could know that Isaac, as a sinner who needs redemption, could not himself be the atoning sacrifice. Furthermore, he knew that God had promised a great nation through Isaac. If Isaac were dead, he could not father a great nation. The implication is that even though Isaac was offered as a sacrifice God could raise him from the dead. As Abraham was about to offer Isaac God stopped him and provided a ram for the offering.
The Tabernacle, and then the Temple, were the appointed sites for these offerings. When the Temple in Jerusalem was finally destroyed by the Romans this created a crisis of meaning for Judaism. If the offering can only be given at the Temple, and the Day of Atonement (among other days) is a central focal point for Judaism, what does it mean to be Jewish without a Temple?
This question is important because of what it indicates about the blessing given to Abraham. The blessing of redemption and knowing God is taught about in the atoning sacrifice. How can the justice of God be fulfilled while the mercy of God also be shown? Can an animal be the actual atoning sacrifice or is it a sign? These questions about atonement will be important for the remaining theistic religions we are studying.