The brief answer to that important question is found in chapter twelve of Genesis. There, the Creator God instructs Abraham (Abram) to “Go out from your country, your relatives, and your father’s household to the land that I will show you. Then I will make you into a great nation, and I will bless you, and I will make your name great, so that you will exemplify divine blessing. I will bless those who bless you, but the one who treats you lightly I must curse, and all the families of the earth will bless one another by your name” (12:1-3).
So yes, the covenant God is demonstrated to have chosen Abraham so that through Abraham the nations and families and the whole of the earth could be blessed. This becomes, for all time, the explicit charge of the covenant people. Naturally, a person that is recognized as a “teacher of Israel” would have been quite familiar with the answer to this question. This, however, it should be recognized, is not a sufficient answer.
The Creator God’s words to Abraham merely beg the question as to “why.” Why did the sovereign God of the cosmos need to choose Abraham? Why did this God have a need or desire to make Abraham into a great nation? Why did the one who, as indicated in the story of Scripture, repeatedly showed Himself as the God of covenants want to bless him? Why make Abraham’s name great? Why was there what seems to be a pressing need to exemplify divine blessing through Abraham? Why is there all this talk of blessing and cursing in association with Abraham? Why indeed?
The reason for all of these things is to be found in what comes before the introduction of Abraham. In the narrative structure, what comes before, of course, is the presentation of the ordering of the creation as the Creator’s cosmic temple, the pronouncement at every stage that this ordering was “very good,” and the placement of man, created as the divine-image, into that creation-as-cosmic-temple so as to steward it, to be a reflection of the glory of its Creator into it, and to stand as a constant reminder to the whole of the creation of its Ruler, that being the Creator God of Israel (Genesis 1 & 2).
This record of the ordering of creation is quickly followed by the report of the divine image-bearers’ first act of idolatry, rebellion, and violation of their God’s commandment. This is swiftly followed by the exile of the now marred image-bearers from the role to which they had been assigned by the Creator. What accompanied this, as pointedly and painfully indicated by Scripture, is the exile of the creation from the condition and state in which it had been created (very good, perfection), as it came to share in the cursing brought about by the one appointed to its rule and stewardship (Genesis 3).
Subsequent to that the first murders are to be found (Genesis 4), along the fathering of a son in the likeness of the fallen image-bearer rather than in the image of the Creator God (Genesis 5), the growing wickedness of the collectively fallen image-bearers (Genesis 6), a worldwide flood of judgment (Genesis 7), the curse of Canaan (Genesis 9), and the culmination of man’s self-idolatry, rebellion, and defiance of the Creator, which was the construction of the Tower of Babel (Genesis 11).
It is at this point that the Creator God is said to have reached down into His creation for the purpose of choosing and appointing Abraham, as something of a project manager charged with the task of the restoration of the fallen creation. Undoubtedly, accurately and purposefully communicating this definitive story would be part and parcel of being a “teacher of Israel,” and it would have to in such a context that Jesus delivers the words of what have come to be the most famous words in the whole of Scripture.