The Messiah would be the descendant of Abraham through whom all nations would be blessed
The beginnings of the Jewish people are found in Genesis 12:1-3. There, God calls Abram (later renamed Abraham) to leave his home country of Mesopotamia for the land that would eventually be called “Israel.” According to Jewish folklore, when he was still back home, Abraham realized that there was only one God and proceeded to demolish the wooden idols in his father’s workshop. That story, though, cannot be found in the Bible, which emphasizes something different: that God brought Abraham to the land of Israel in order to do three things. First, God would make a great people from Abraham, later specified to be from Abraham’s son Isaac (rather than Ishmael), and Isaac’s son Jacob (rather than Esau). From Abraham, Isaac, and Jacob have come the Jewish people. To this day, Jewish liturgy refers to “the God of Abraham, Isaac, and Jacob.”
The second promise was of the land itself, and both these first two promises are reiterated in Genesis 15 and later chapters.
The third promise was that through Abraham and his descendants, all the nations of the world would be blessed. This promise, among others, is repeated in Genesis 18:17-18: “The LORD said, ‘Shall I hide from Abraham what I am about to do, seeing that Abraham shall surely become a great and mighty nation, and all the nations of the earth shall be blessed in him?’”
It has always been the biblical hope that one day the nations of the world would join with Israel in worshiping the God of Abraham, Isaac, and Jacob. One can make a good case that through Jewish doctors, lawyers, scientists, and the world-renowned Israeli technology sector, great blessing has already come to the world. But as the Bible shows us, the ultimate fulfillment is that through Jesus, many nations of the world that formerly practiced pagan religions have now come to know the living God. And of course, the Jewish people themselves are included in this blessing.
In the New Testament book of Acts 3:24-26, one of Jesus’ followers Peter speaks to a crowd of his fellow Jews on the holiday of Shavuot: “All the prophets who have spoken, from Samuel and those who came after him, also proclaimed these days. You are the sons of the prophets and of the covenant that God made with your fathers, saying to Abraham, ‘And in your offspring shall all the families of the earth be blessed.’ God, having raised up his servant, sent him to you first, to bless you by turning every one of you from your wickedness.”
That’s it in a nutshell. God raised up His servant Jesus the Messiah (described in Isaiah 53) to fulfill the promises God made to the patriarchs Abraham, Isaac and Jacob. This fulfillment comes through Jesus, through whom Israel and the nations receive the blessing of atonement for sins (“turning every one of you from your wickedness”) and the knowledge of God Himself. And it all started in Genesis 12:3.