The burden of Paul in Romans 11 is the salvation of Israel. Not only "some of them," as it says in verse 14, but in the end the whole people. "A partial hardening has come upon Israel, until the fullness of the Gentiles has come in. vs 26 And in this way all Israel will be saved" 

God's purpose in the trespass of Israel is salvation for the Gentiles. And his purpose for the salvation of the Gentiles is to make Israel jealous, so that she (Israel) awakens to the greatness of Christ and embraces her Messiah. And then Paul adds, the purpose of the salvation of all Israel "their full inclusion" is something even greater. Something glorious follows the full number of the Gentiles and the full number of Israel. For if Israel's rejection means the reconciliation of the world, what will their acceptance mean but life from the dead? 

"God has not rejected his people whom he foreknew" (Romans 11:2). My friends, God's word has not fallen short. And if you will trust him and bank on his Son Jesus Christ, all the promises of God for living and dying will be yours and will be unquestionable. 

And how can they believe in him if they have never heard about him? And how can they hear about him unless someone tells them?  And how will anyone go and tell them without being sent?

That if you confess with your mouth the Lord Jesus and believe in your heart that God has raised Him from the dead, you will be saved. 10 For with the heart one believes unto righteousness, and with the mouth confession is made unto salvation

"Wretched man that I am! Who will deliver me from this body of death? Thanks be to God through Jesus Christ our Lord!" He is our righteousness. He is our victory. He has circumcised our hearts. And he is working our sanctification.

 You see, God’s purpose for the law reaches its climax when the Messiah arrives; now all who trust in Him can have their lives made right with God.  Jesus Christ is the Fulfillment of the Law! 

Isa 28:16 “Look what I am going to do in Zion.
I’ll put in place a stone that makes them stumble, a rock that trips them up, but those who trust in it will not be disgraced” 

In his absolute, glorious freedom — “I’ll have mercy on whom I have mercy; I’ll be gracious to whom I’ll be gracious” — he makes known the riches of his glory for the vessels of mercy. That’s verse 23, and that’s the ultimate goal of the universe. Those vessels of mercy are prepared beforehand by God for glory.

But in this very moment, the vessels of mercy are everyone and anyone who calls on the name of the Lord.

The matter gave great pain to Abraham—after all, Ishmael was his son. But God spoke to Abraham, “Don’t feel badly about the boy Ishmael or about Hagar your maid servant. Do whatever Sarah tells you. Your descendants will come through Isaac. Regarding your maid’s son, be assured that I’ll also develop a great nation from him—he’s your son, too.”  Genesis 21:12