Have they stumbled that they should fall? - Have the Jews, now for their disobedience and unbelief rejected, so sinned against God as to be for ever put out of the reach of his mercy? By no means. Are they, as a nation, utterly irrecoverable? This is the sense of the place, and here the prophecy of the restoration of the Jewish nation commences.

But rather through their fall salvation is come - The Church of God cannot fail; if the Jews have broken the everlasting covenant, Isaiah 24:5, the Gentiles shall be taken into it; and this very circumstance shall be ultimately the means of exciting them to seek and claim a share in the blessings of the new covenant; and this is what the apostle terms provoking them to jealousy, i.e. exciting them to emulation, for so the word should be understood. We should observe here, that the fall of the Jews was not in itself the cause or reason of the calling of the Gentiles; for whether the Jews had stood or fallen, whether they had embraced or rejected the Gospel, it was the original purpose of God to take the Gentiles into the Church; for this was absolutely implied in the covenant made with Abraham: and it was in virtue of that covenant that the Gentiles were now called, and not Because of the unbelief of the Jews. And hence we see that their fall was not the necessary means of the salvation of the Gentiles; for certainly the unbelief of the Jews could never produce faith in the Gentiles. The simple state of the case is: the Jews, in the most obstinate and unprincipled manner, rejected Jesus Christ and the salvation offered them in his name; then the apostles turned to the Gentiles, and they heard and believed. The Jews themselves perceived that the Gentiles were to be put in possession of similar privileges to those which they, as the peculiar people of God, had enjoyed; and this they could not bear, and put forth all their strength in opposition and persecution. The calling of the Gentiles, which existed in the original purpose of God, became in a certain way accelerated by the unbelief of the Jews, through which they forfeited all their privileges, and fell from that state of glory and dignity in which they had been long placed as the peculiar people of God. See Taylor.

Have they stumbled.

Ezekiel 18:23,32 Have I any pleasure at all that the wicked should die? said the Lord GOD: and not that he should return from his ways, and live...

Ezekiel 33:11 Say to them, As I live, said the Lord GOD, I have no pleasure in the death of the wicked...

but rather.

Romans 11:12,31 Now if the fall of them be the riches of the world, and the diminishing of them the riches of the Gentiles...

Acts 13:42,46-48 And when the Jews were gone out of the synagogue, the Gentiles sought that these words might be preached to them the next sabbath...

Acts 18:6 And when they opposed themselves, and blasphemed, he shook his raiment, and said to them, Your blood be on your own heads; I am clean...

Acts 22:18-21 And saw him saying to me, Make haste, and get you quickly out of Jerusalem: for they will not receive your testimony concerning me...

Acts 28:24-28 And some believed the things which were spoken, and some believed not...

for.

Romans 11:14 If by any means I may provoke to emulation them which are my flesh, and might save some of them.

Romans 10:19 But I say, Did not Israel know? First Moses said, I will provoke you to jealousy by them that are no people...

to provoke them to jealousy. Rather 'to provoke (or excite) them to emulation,' [parazeloo,] as it is rendered.

Spiritual Blindness.
"As it is written, God hath given them the spirit of slumber, eyes that they should not see, and ears that they should not hear."--ROMANS xi. 8. "Blindness in part is happened to Israel."--ROMANS xi. 25. It is a sad and painful reflection, and one which is continually forced upon us as we read the New Testament, that the long training and preparation of the Jews brought them at the last not to the acceptance but to the rejection of Jesus. They had been taught, generation after generation, that they …
John Percival—Sermons at Rugby

The Sovereignty of God in Operation
"For of Him, and through Him, and to Him, are all things: to whom be the glory for ever. Amen" (Romans 11:36). Has God foreordained everything that comes to pass? Has He decreed that what is, was to have been? In the final analysis this is only another way of asking, Is God now governing the world and everyone and everything in it? If God is governing the world then is He governing it according to a definite purpose, or aimlessly and at random? If He is governing it according to some purpose, then …
Arthur W. Pink—The Sovereignty of God

Reprobation Asserted: Or, the Doctrine of Eternal Election and Reprobation Promiscuously Handled, in Eleven Chapters.
WHEREIN THE MOST MATERIAL OBJECTIONS MADE BY THE OPPOSERS OF THIS DOCTRINE, ARE FULLY ANSWERED; SEVERAL DOUBTS REMOVED, AND SUNDRY CASES OF CONSCIENCE RESOLVED. BY JOHN BUNYAN OF BEDFORD, A LOVER OF PEACE AND TRUTH. 'What then? Israel hath not obtained that which he seeketh for; but the election hath obtained it, and the rest were blinded.'--Romans 11:7 London: Printed for G. L., and are to be sold in Turn-stile-alley, in Holbourn. Small 4to, 44 pages. EDITOR'S ADVERTISEMENT. This valuable tract …
John Bunyan—The Works of John Bunyan Volumes 1-3