Romans 11:11-12 — I say then, Have they stumbled that they should fall? God forbid: but rather through their fall salvation is come unto the Gentiles, for to provoke them to jealousy.
Now if the fall of them be the riches of the world, and the diminishing of them the riches of the Gentiles; how much more their fulness?
See Romans 10:19 with the quote from Deuteronomy 32:21.
stumble — over Christ, their stumbling stone (the table in verse 9)
fall — without hope of recovery (first usage)
fall — moral trespass (second usage) as in Romans 5:15
If Israel's fall brought the riches of the gospel to the world, how much more will the world benefit from Israel's restoration (fullness)?
fullness — The entire nation will be saved and not just a remnant, as now — full and national prosperity. God shall bless us; and all the ends of the earth shall fear Him (Psalm 67:7).
diminishing — national importance and spiritual and numerical loss. And ye shall be left few in number, whereas ye were as the stars of heaven for multitude; because thou wouldest not obey the voice of the LORD thy God (Deuteronomy 28:62).
While the Apostle's chief purpose in Chapter 11 is to prove that God is not "through with Israel" as the spiritualizers teach, it is enlightening to consider what he says here regarding the blessing of the Gentiles during this present dispensation of the grace of God. Let us consider this in the light of its background.
According to all covenant and prophecy, the Gentiles were — and are — to be blessed through the rise of Israel. Note only the two following passages so Scripture:
That in blessing I will bless thee, and in multiplying I will multiply thy seed as the stars of the heaven, and as the sand which is upon the sea shore; and thy seed shall possess the gate of his enemies; and in thy seed shall all the nations of the earth be blessed; because thou hast obeyed My voice (Genesis 22:17-18).
Arise, shine; for thy light is come, and the glory of the LORD is risen upon thee. For, behold, the darkness shall cover the earth, and gross darkness the people: but the LORD shall arise upon thee, and His glory shall be seen upon thee. And the Gentiles shall come to thy light, and kings to the brightness of thy rising (Isaiah 60:1-3).
This will take place at a future time, but surely it is not happening today …
Whereas Israel, according to the prophecy, is to be given supremacy over the nations (Isaiah 60:10-12; 61:6), this is clearly not so today. Israel as a nation has been cast out of God's favor, as the Gentiles had been many centuries before, but both Jews and Gentiles as individuals are now offered reconciliation by grace through the shed blood of Christ (2 Corinthians 5:14-21).
According to covenant and prophecy, the Gentiles are to be blessed through Israel's instrumentality (Genesis 22:17-18; Zechariah 8:13), but today they are being blessed through Israel's obstinacy (Acts 13:44-46; Romans 11:28-32).
According to prphecy the Gentiles are to be bless through Israel's rise (Isaiah 60:1-3; Zecharaiah 8:22-23). But today the Gentiles are being blessed through her fall (Romans 11:11).
Thus the salvation of Gentiles — and Jews — today is not based on any covenant but only on God's grace; not on the fulfillment of any prophecy, but upon His eternal purpose, the mystery … kept secret since the world began, but made known in due time through the Apostle Paul (Romans 11:25; Ephesians 3:1-4). — C.R. Stam, The Epistle of Paul to the Romans, pages 276-277.