do not boast over the branches. If you do boast, remember that it is not you that support the root, but the root that supports you.
You will say, "Branches were broken off so that I might be grafted in."
That is true. They were broken off because of their unbelief, but you stand only through faith. So do not become proud, but stand in awe.
For if God did not spare the natural branches, perhaps he will not spare you.
References for Romans 11:21
Note then the kindness and the severity of God: severity toward those who have fallen, but God's kindness toward you, provided you continue in his kindness; otherwise you also will be cut off.
And even those of Israel, if they do not persist in unbelief, will be grafted in, for God has the power to graft them in again.
References for Romans 11:23
For if you have been cut from what is by nature a wild olive tree and grafted, contrary to nature, into a cultivated olive tree, how much more will these natural branches be grafted back into their own olive tree.
So that you may not claim to be wiser than you are, brothers and sisters, I want you to understand this mystery: a hardening has come upon part of Israel, until the full number of the Gentiles has come in.
References for Romans 11:25
And so all Israel will be saved; as it is written, "Out of Zion will come the Deliverer; he will banish ungodliness from Jacob."
"And this is my covenant with them, when I take away their sins."
As regards the gospel they are enemies of God for your sake; but as regards election they are beloved, for the sake of their ancestors;
References for Romans 11:28