Among the many texts that demonstrate that Israel indeed has a vocation is this text from Romans 2:
But if you bear the name "Jew" and rely upon the Law and boast in God, 18and know His will and approve the things that are essential, being instructed out of the Law, 19and are confident that you yourself are a guide to the blind, a light to those who are in darkness,
Paul knows his Old Testament – he is evoking the image of Israel as a light to the pagan nations. Remember the context here in Romans 2: Paul is lecturing the Jew who thinks he is superior to the Gentile (this can be easily shown by what Paul goes on to say later in Romans 2 where he speaks of Gentiles judging Jews). This text, from Isaiah 42, places the “servant” in the position of being the one who is a “light” to the pagan nations:
Behold, My Servant, whom I uphold;
My chosen one in whom My (D)soul delights
I have put My Spirit upon Him;
He will bring forth justice to the nations.
2"He will not cry out or raise His voice,
Nor make His voice heard in the street.
3"A bruised reed He will not break
And a dimly burning wick He will not extinguish;
He will faithfully bring forth justice.
4"He will not be disheartened or crushed
Until He has established justice in the earth;
And the coastlands will wait expectantly for His law."
5Thus says God the LORD,
Who created the heavens and stretched them out,
Who spread out the earth and its offspring,
Who gives breath to the people on it
And spirit to those who walk in it,
6"I am the LORD, I have called You in righteousness,
I will also hold You by the hand and watch over You,
And I will appoint You as a covenant to the people,
As a light to the nations,
Before anyone baldly claims that this is about Jesus to the exclusion of Israel, note what Isaiah has said just one chapter back about the identity of the servant:
But you, Israel, My servant,
Jacob whom I have chosen,
Descendant of Abraham My friend,
And then in chapter 43, Isaiah places Israel squarely in the role of a servant who brings light to the pagan nations:
But now, thus says the LORD, your Creator, O Jacob,
And He who formed you, O Israel,
"Do not fear, for I have redeemed you;
…..
Bring out the people who are blind, even though they have eyes,
And the deaf, even though they have ears.
9All the nations have gathered together
So that the peoples may be assembled
Who among them can declare this
And proclaim to us the former things?
Let them present their witnesses that they may be justified,
Or let them hear and say, "It is true."
"You are My witnesses," declares the LORD,
"And My servant whom I have chosen,
So that you may know and believe Me
Note the echoes of Paul’s indictment of the Jew in Roman 2. Paul says that the Jew was to be a light to the blind. Understood in the Biblical context, as these Isaiah text show, Paul is making is a clear allusion to the role that Israel is supposed to perform – being a light to the pagans, so that the pagans can know that YHWH is the true God.
This is but one of many scriptural arguments that Israel indeed has a vocation. And it goes beyond this – Paul is indicting the Jew for failing to live up to his covenantal obligation.
And, as we will shortly see, Paul understands that Jesus acts as Israel, fulfilling her covenantal obligation to be light to the nations.