I'm continuing to turn the soil to reformulate, refine, and revise subsequently. Today I'm asking how Moses and the Law might have served mediating roles between God and Israel.
For Moses, there is of course his role in mediating the exodus. God sends him to Pharaoh (Exod. 3:10) and to Israel (3:13). God makes him as a god to Pharaoh, thus mediating God's authority to Pharaoh (7:1). Moses' role in these pages is very prophet-like in some ways.
Indeed, Deuteronomy 18:15 predicts the future rise of a "prophet like me." Regardless of who Deuteronomy originally had in mind, the passage clearly categorizes Moses as a prophet, in whom God "will put my words in the mouth of the prophet, who shall speak to them everything that I command" (Deut. 18:18). Many scholars (although probably not evangelical ones) think this might have originally referred to Josiah. If so, the passage leans toward a "king-prophet" type. Certainly when we take the passage in relation to Christ, this is the case.
Exodus 20:18-21 gives us a striking picture of Moses as mediator between God and Israel, striking in that the people beg Moses to be the one who talks to God. They are afraid of the thunder and lightning coming from the mountain. Deuteronomy 5:5 refers to the same event, saying, "At that time I was standing between the LORD and you to declare to you the words of the LORD; for you were afraid because of the fire and did not go up the mountain."
Leviticus 26:46 is quite straightforward about Moses as mediator of the law: "These are the statutes and ordinances and laws that the LORD established between himself and the people of Israel on Mount Sinai through Moses." The wording is very similar to Galatians 3:46, so Moses is the mediator through whom the Law came.
So Moses was a foundational mediator between God and Israel. God used Moses to lead Israel out of Egypt. God used Moses to reveal the Law to Israel. The people relied on Moses to mediate these things because they were afraid. These roles are primarily prophetic, but at the same time lean a little toward the kind of mediation a king would provide for a people in relation to God.
At the same time, Moses interceded for the people as well, just as Abraham interceded for Sodom and Gomorrah. This is a prophetic function as well.
When Israel had sinned with the Golden Calf, Moses pleaded with God not to destroy them (Exod. 32:11-14). Moses suggests that God doesn't want the Egyptians to be able to speak ill of God if He should destroy Israel in the desert. Moses reminds God of His promises to Abraham, Isaac, and Jacob. In result, the LORD changes His mind (Exod. 32:14).
[By the way, this is high anthropomorphism from a Christian standpoint, although we have no reason to think the ancient Israelites might not have understood it literally. From a Christian standpoint, an omniscient God always knew these things would happen and can't be reminded of things by a human]
The Law itself was key to Israel's relationship with God, particularly in the post-exilic period. The evidence we have from Judges, Samuel, and Kings suggests that the Law played a negligible role in the life of Israel until the days of Josiah, and even then it is probably the book of Deuteronomy that began to take on a normative role.
In particular, Deuteronomy 28 sets out an extensive list of blessings and curses that follow in consequence of Israel either keeping or violating the law. The deuteronomistic history of Joshua, Judges, Samuel, and Kings understands the vicissitudes of Israel's fortune in the particular light of whether Israel served other gods or not.
From the time of Ezra's reforms, however, the Law in its fuller Exodus-Leviticus form seems to come into fuller play. Jeremiah 7:22 seems to imply that Jeremiah knows nothing of Levitical law at the hands of Moses. Malachi in particular (400's) refers finally to the statutes delivered to Moses (notice the striking absence of such rhetoric in the pre-exilic prophets and books like Judges, Samuel, and Kings). The Sabbath also seems suddenly to become more important from the late exile on.
In the intertestamental period, high priest seem to have become the focus of political and religious power in Israel. In that sense, the primary role of mediation between God and humanity came through a priestly channel. But it was probably not until the Maccabean period that the Law as we think of it took on full force within Palestinian Jewish life, and even then probably only in certain sects like the Hasidim (who become the Pharisees) and the Enochics (who become the Essenes).
The Sadducees are probably the heirs of the temple priestly class displaced by the Maccabean priests (the Hasmoneans). Since the roots of the Diaspora are prior to this period, we should not be surprised to find forms of Judaism outside Palestine that surprise us, such as the Jews at Elephantine who had a temple of their own. Even within Palestine the Samaritans had their own version of the Pentateuch and had no sense of obligation to the Jerusalem temple.
Although we can question how extensive E. P. Sanders' "covenantal nomism" was within Judaism. It certainly does describe some of the sects we mention above. For these, the Law in its canonical form was seen as the mediating factor between God and Israel. If Israel kept the Law, God would restore her land to her. If not, Israel's enslavement to the Romans would continue.