I love Romans 10:20-21:
Then Isaiah is so bold as to say,
"I have been found by those who did not seek me;
I have shown myself to those who did not ask for me."
But of Israel he says, "All day long I have held out my hands to a disobedient and contrary people."
Here is a twofold display of grace that Paul spends chapter 11 unpacking. Jesus has been found by those who did not seek Him. Jesus has revealed Himself to a people that were not looking. Salvation has come to the gentiles! Aren't you glad about that? Listen up ethnic factions in the Roman church, the Gospel has come to the Gentiles. And not just to the ones that were looking, Paul quotes Isaiah saying that He's come to a people who did not seek or ask for Him. This is of course true on a micro level as well. None of us were seeking or asking for Him when he saved us...He saved us because He saved us, but here Paul draws it out to it's glorious multi ethnic Gospel level... Salvation has come to the Gentiles!
How has this happened? The gentiles have been grafted in. The wild olive branches have been attached to the natural tree, the original branches cut off. Should this make gentiles proud? By no means it should have us in awe, if God cut off the original branches, will He not also cut off any non abiding unnatural branches? Of course! How is this grace twofold though? How does God 'all day long hold out His hands to a disobedient and contrary people?'
Well in Isaiah's context He sent to prophets, the His Son, and now He has grafted the gentiles in to make the Jews jealous (11:11). Just as there was a remnant in Elijah's day, so there is today. All Israel will be saved. The faithful remnant will be bought in, the Jews with all their natural, historical, covenant advantages will be saved. A partial hardening on Israel, then the fullness of the Gentiles, then all Israel (11:26)
So then. Stand in awe (11:20) Be amazed that branches were cut off that you might, that we might, be grafted in. Don't be arrogant about it, but humbled. Be amazed at God's twofold, complete, grace, He doesn't forget His people, but neither does He forget all who He has made.
Paul is probably addressing a factioning in the Roman church, which is why he goes onto write about fulfilling the law though love.(13:8-14) But there is much for us to be humbled about here as gentiles, and much for us to be excited about as 'all Israel will be saved' will only mean good things for us (11:12).