Introducing the mediator

Our Bible Study group discussed Genesis 18 this past week, and the presenter introduced an interesting concept: That of Abraham in the role of mediator.

God comes down to earth and is passing by Abraham's tent, and the message is given again that Sarah will have a child. Now, Abraham had already been told this in the previous chapter, so it follows that God didn't come down just for this reason. And indeed, they then carry on towards Sodom and Gomorrah, and God tells Abraham of His intent to determine the truth of the sinfulness of those cities so that He may wipe them out.

Now we've seen this happen already a few times previous to now. God comes down "in the cool of the day" after Adam and Eve sin; God knows what they did, but He's come down to confront them and bring judgment. When Cain kills Abel, God again comes and speaks to Cain, saying that Abel's blood is crying out from the ground. God also comes down to see the Tower of Babel and to render judgment. However, this time things are different.

God is coming to judge Sodom and Gomorrah, but He stops at Abraham's tent. Why? Because He is establishing the role of the mediator, which Abraham is the first to carry out. He's here to bring judgment, but also so that Abraham  will intercede and understand his duty, a duty that will be passed down through generations to Israel and beyond.

Another interesting point is that the message of the birth is stated *again* here. Abraham already knew about this promise, so on one hand this is God saying it to Sarah as well. But additionally I think this is symbolic of the eventual promise of the covenant fulfillment in the coming of Christ.
Essentially, God is coming in judgment against a people, but establishing that there is mediation and that the righteous will have mercy. Then God is giving a message, as He does all throughout Israel's history, of judgment for sin but a promise of mercy through the seed of the woman in the future.

(Hopefully this makes sense, it's taken from notes. I just find it intriguing that this is sort of the next step in the covenant promise God made to Abraham, which establishes God's people as mediators and ministers to the nations, and looks to the hope of Christ)