The Self-Donation of God, pg. 33:
"In subsequent Israelite history prophetic mediatorship was also unsuccessful. In spite of this, we find the promise of the eschatological fulfillment of prophetic mediatorship throughout the Old Testament. In the farewell address of Deuteronomy 18, Moses prophesies of the coming of a prophet like himself, in whose mouth God will place his words (Deut 18:18). The book of Deuteronomy and the so-called Deuteronomistic history emphasize, God is present in his Word and in his Name, and therefore the implication is that this prophet will mediate the divine presence. It also follows that this prophet must be greater than Moses and therefore must mediate the divine presence in an even greater manner than he did. If he were not greater, then Moses’ mediation would have sufficed. Taking this reasoning one step further, we must posit that the coming of this prophet represents the coming of God himself. If Moses spoke with God "face to face" (Exod 33:11) and a prophet is measured by his closeness to God and his ability to mediate the divine (Num 12:6-8), then the only possibility for a greater revelation of God would be the coming of God himself.
Isaiah understands this coming of a prophet like Moses to be the coming of the Servant of YHWH, who is himself YHWH. We are first informed that the Lord himself is personally returning to Zion (Isa 40), thereby reversing the state of exile. This returning “glory” will be seen by “all flesh” (40:5). This returning presence is clearly identical with the Servant of the Lord. He is God's luminous glory in that he is a "light to the nations"(49:6). This description clearly parallels the universal manifestation of the kavod in 40:5. Furthermore he is described as the "arm of the Lord"(53:1, 63:12). He is also the "Angel of the presence" sent to save (63:9).
If Isaiah describes a new exodus, then there must logically also be a new Moses and a new Passover lamb. Just as Moses sprinkled Israel with the blood of the covenant (Exod. 24:8), so the Servant will "sprinkle many nations" (Isa 52:15) and will not only establish a covenant, but himself will be a "covenant for the people" (42:6). In light of the fact that the redeeming promise of grace ends the exile which has occurred because of sin, this covenant can be none other than the new covenant spoken of by Jeremiah which eliminates sin. God tells the prophet that the former covenant that he made with Israel after leading them out of Egypt was nonfunctional because of the unbelief and disobedience of the nation (Jer 31:31-2). Echoing Moses' own prediction in Deuteronomy 30:6, ("And the LORD your God will circumcise your heart and the heart of your offspring, so that you will love the LORD your God with all your heart and with all your soul, that you may live."), Jeremiah states that YHWH will make a new covenant (v. 31): “I will make with the house of Israel after those days, declares the LORD: I will put my law within them, and I will write it on their hearts.” (31:33) and "[f]or I will forgive their iniquity, and I will remember their sin no more" (v. 34). Moses tried to place the law within the Israelites’ hearts (Deut 6:6), but he could only demand and coerce them into imprinting it on themselves in an outward way (6:8-9). In the same manner, Moses established sin-offerings (Lev 4:1-5:13, 6:24-30, 8:14-17, 16:3-22) and guilt offerings (Lev 5:14-6:7, 7:1-6) which could not ultimately cleanse the conscience (Heb. 10:4). The result of this unatoned for sin would be exile, as Moses himself predicts in Deuteronomy 27-32. The word and works of the Servant will accomplish the end of exile, and therefore finally eliminate sin.
Moreover, the nineteenth century Lutheran Old Testament scholar Ernst Hengstenberg, points out that the Servant does not merely mediate the covenant like Moses, but in fact is the covenant himself. He can do this because he is the one who has become the new Passover lamb and true sin offering (Isa 53:5, v. 7,10). He will for the sake of his people be "distressed" with their “distress” (63:9) (or possibly one could translate this as “afflicted” with their “affliction”). The Servant proclaims this universal Jubilee (Isa 61:2), based on the new covenant's forgiveness of sins (Jer. 31:34) rooted in his own person and work. Moses attempted to redeem Israel by doing this (Exod 32:31-2), but was unable."