Romans 11

 Paul presents the "mystery" of God's "unsearchable.. judgements and unfathomable...ways" ( v25,33) :

God has made a choice to preserve a "remnant" among the Jews by His grace.  He chose "those He foreknew"... and they have obtained that grace by faith, not by works.

All others have been "hardened". ( petrified like stone, blinded, callous) .  Their eyes do not see and their ears do not hear the Word.
Paul says that this is not God's total rejection of Israel - it is a stumble, not a fall...
"But by their transgressions salvation has come to the Gentiles to make them jealous." ( v11)

If their transgression brings about good for the Gentiles, Paul argues, how much more wonderful will their salvation be! When Israel is reconciled to God it will be all the more glorious!

Paul gives an interesting parable to further explain this mystery ..
The "rich root of the olive tree" - is holy and that which supports all the branches.  Jesus!!!
The Jews are the original branches of this tree, but some have been broken off "for their unbelief". 
The Gentiles who came to faith in Jesus are like wild olive branches that have been grafted into the rich root - into Jesus.  
It is by God's kindness that we are grafted into the Root - into Jesus.
It is only by faith in God's kindness and grace that this happened and that we continue to remain in Him.
God is not done with the Jews, however... they may still be grafted back into the Root, just as easily as we, the wild olive branches, were also grafted in.

Paul considers the hardening of the Jews' hearts as a "partial hardening" until "the fulness of the Gentiles has come in". ( v25)
There will come a time when God will fulfill all His promises to Israel for they "are beloved for the sake of the fathers;"  God chose them for Himself and He will  do all that He has said.
Until that time, we must remember that their disobedience has led to God's mercy on us.
Therefore we must not be arrogant.. but thankful..

We all have been shown God's mercy!

" How unsearchable are His judgements and unfathomable His ways!"

Father in heaven, Your wisdom and knowledge are unsearchable!  The riches of Your grace and mercy are unfathomable.  We cannot begin to grasp this great mystery of Your plan of salvation for both the Jews and the Gentiles.  We praise You that everything is from You, through You, and to You. To You be glory and honor and praise. Because of Your mercy, we are saved.. set free from death and sin and the law.. we are grafted into the divine Root - into Jesus Christ our Lord.  Thank You gracious God and Redeemer. Amen.