For God is able, etc. Frigid would this argument be to the profane; for however they may concede power to God, yet as they view it at a distance, shut up as it were in heaven, they do for the most part rob it of its effect. But as the faithful, whenever they hear God's power named, look on it as in present operation, he thought that this reason was sufficient to strike their minds. We may add, that he assumes this as an acknowledged axiom, -- that God had so punished the unbelief of his people as not to forget his mercy; according to what he had done before, having often restored the Jews, after he had apparently banished them from his kingdom. And he shows at the same time by the comparison, how much more easy it would be to reverse the present state of things than to have introduced it; that is, how much easier it would be for the natural branches, if they were again put in the place from which they had been cut off, to draw substance from their own root, than for the wild and the unfruitful, from a foreign stock: for such is the comparison made between the Jews and the Gentiles.

And they also - The Jews.
If they bide not - If they do not continue in willful obstinacy and rejection of the Messiah. As their unbelief was the sole cause of their rejection, so if that be removed, they may be again restored to the divine favor.
For God is able - He has,
(1) Power to restore them, to bring them back and replace them in his favor.
(2) he has not bound himself utterly to reject them, and forever to exclude them.
In this way the apostle reaches his purpose, which was to show them that God had not cast away his people or finally rejected the Jewish nation; Romans 11:1-2. That God has this power, the apostle proceeds to show in the next verse.

If they abide not in unbelief - So, we find that their rejection took place in consequence of their wilful obstinacy: and, that they may return into the fold, the door of which still stands open.
For God is able to graft them in again - Fallen as they are and degraded, God can, in the course of his providence and mercy, restore them to all their forfeited privileges; and this will take place if they abide not in unbelief: which intimates that God has furnished them with all the power and means necessary for faith, and that they may believe on the Lord Jesus whenever they will. The veil now continues on their heart; but it is not a veil which God has spread there, but a veil occasioned by their own voluntary and obstinate unbelief: and, when they shall turn to the Lord, (Jesus), the veil shall be taken away. See what the apostle has said, 2-Corinthians 3:6-18.

(12) And they also, if they abide not still in unbelief, shall be graffed in: for God is able to graff them in again.
(12) Many are now for a season cut off, that is, are without the root, who in their time will be grafted in: and again there are a great number who after a certain manner, and with regard to the outward show seem to be ingrafted, who nonetheless through their own fault afterwards are cut off, and completely cast away: which thing is especially to be considered in nations and peoples, as in the Gentiles and Jews.

And they also, if they abide not still in unbelief,.... The apostle suggests that the Jews also might be recovered and brought into a Gospel church state, provided they did not continue in infidelity; but inasmuch as they seem to lie under invincible ignorance, obstinacy, and unbelief, and were such bitter enemies to the Gospel, and abhorrers of Gospel ordinances, and a Gospel church state; yea, that they must and will abide in unbelief, unless the Spirit of God convinces them of it, and it is given to them to believe in Christ, and they are powerfully drawn by the Father to come to the Son, there is no possibility or likelihood that they
shall be grafted in, or taken into a Gospel church state; to which the apostle answers, and argues for their ingrafting, and the possibility of it from the power of God:
for God is able to graft them in again; as many of them were in the times of the apostles, and some since, for nothing is impossible with God; he can remove their unbelief, knock off the shackles and fetters in which they are held, and bring, them out of the prison of infidelity, in which they are shut up; he is able to take away the blindness of their minds, and the hardness of their hearts, the veil that is over them, and turn them to the Lord; he can by his mighty power work faith in them, and cause them to look on him whom they have pierced, and mourn in an evangelical manner; he can bring them to Christ, and into his churches, and among his people, and fold them with the rest of his sheep; so that there one fold of Jew and Gentile, under one shepherd, Jesus Christ.

And they also--"Yea, and they"
if they abide not still in unbelief, shall be grafted in: for God is able to graft them in again--This appeal to the power of God to effect the recovery of His ancient people implies the vast difficulty of it--which all who have ever labored for the conversion of the Jews are made depressingly to feel. That intelligent expositors should think that this was meant of individual Jews, reintroduced from time to time into the family of God on their believing on the Lord Jesus, is surprising; and yet those who deny the national recovery of Israel must and do so interpret the apostle. But this is to confound the two things which the apostle carefully distinguishes. Individual Jews have been at all times admissible, and have been admitted, to the Church through the gate of faith in the Lord Jesus. This is the "remnant, even at this present time, according to the election of grace," of which the apostle, in the first part of the chapter, had cited himself as one. But here he manifestly speaks of something not then existing, but to be looked forward to as a great future event in the economy of God, the reingrafting of the nation as such, when they "abide not in unbelief." And though this is here spoken of merely as a supposition (if their unbelief shall cease)--in order to set it over against the other supposition, of what will happen to the Gentiles if they shall not abide in the faith--the supposition is turned into an explicit prediction in the verses following.