Paul’s transition from Chapter 8 is quite abrupt.  This sudden change may be accounted for psychologically.  Paul had just been contemplating the certainty of the glory of the sons of God; but his heart goes now to the other extreme, the failure and misery of his own countrymen.  The strong language that he uses in this chapter was necessary because, in giving the Gospel to the heathen, Paul was looked upon by the Jews as a traitor and enemy of his own people.
         Notice that Paul never mentions their rejection; a subject that obviously was extremely painful to his thoughts.  But it is very evident that his arguments in this chapter rest on the supposition that the main body of the Jewish nation would be cast out of the visible Kingdom of God; and it is for this reason that in these next three chapters he considers the reception of any people into the kingdom and covenant of God under the relative notion of inviting and choosing, or of calling and election.  The Jews were rejected and reprobated; the Gentiles were chosen and called, or elected.  As this is most obviously Paul's meaning, it is strange that any should apply his doctrine to the particular and unconditional reprobation and election of individuals.
         It is upon this rejection of the Jews that the calling and election of the Gentiles rest.  If the Jews be not rejected, but are still Kingdom of God, then the Gentiles, according to the most proper inference from Paul’s doctrine, have no right to the blessings of the kingdom. Apart from being invited or called, they are intruders at the heavenly feast.
         And all this was intended at once to vindicate the Divine dispensations; to convince the infidel Jew; to satisfy the believing Gentile that his calling or invitation into the Church of God was valid; to arm him against the carping and objections of the unbelieving Jews, and to dispose the Christian Jew to receive and own the believing Gentile as a member of the family and kingdom of God, by Divine right, equal to any to which he himself could pretend.

“I say the truth in Christ, I lie not, my conscience also bearing me witness in the Holy Ghost,”
Paul is revealing the intense pain with which he contemplates the unbelief of his countrymen. The discussion of the case of Israel occupies this chapter and the next two chapters.

         “I say the truth”
         Literally:  “I tell {the} truth.”–In our vernacular we would say, “What I am saying is the truth.”

 In what I am about to affirm respecting my attachment to the nation and people. Most interpreters regard this as a form of an oath; being equivalent to Paul calling Christ as his witness. It is certainly to be regarded, in its obvious sense, as an appeal to Christ as the Searcher of the heart, and as the judge of falsehood.

         “in Christ”–Not by Christ, as the formula of an oath. The word translated as “in” (Grk.–en) is also used in the form of an oath in Matt. 5:34-36; Rev. 10:6.  For this favorite expression of Paul     see Gal. 2:17; I Cor. 1:2; II Cor. 1:14, 17, 11:19.

         “my conscience bearing me witness
         Literally: “My conscience bearing witness with me.”–Concurring with my testimony. 

My conscience is testifying to the truth of what I say.  As to the truth of what I say; in the Holy Spirit, Who searches all hearts, and perfectly knows whether the soul on which he operates be sincere.

         CONSCIENCE:  (suneidēseōs)–Literally: “conscience; awareness.”  Conscience is that act of judgment of the mind by which we decide on the lawfulness or unlawfulness of our actions, and by which we instantly approve or condemn them. It exists in every man, and is a strong witness to our integrity or to our guilt.

Here, as in 2:15, we have much in the modern sense of the word; the introspective faculty which sits in judgment upon actions, and assigns to them their moral qualities of praise or blame.  As if in our vernacular Paul might be saying,  “This conscience of mine is being also overshadowed with the Holy Spirit, and therefore incapable of falsehood or self-deception.”

         “in the Holy Ghost”
         Literally: “In {the} Holy Spirit.”–Under His direction and influence. Through His grace. 

Paul is saying that his conscience pronounced its concurring testimony by the Holy Spirit; that is, conscience as enlightened and influenced by the Holy Spirit.  Here we find that the testimony of the man's own conscience, and the testimony of the Holy Spirit, are two distinct things, and that Paul had both at the same time. Paul’s affirmation is made so solemn because the Jews charged him with having forsaken his race. He speaks as in the presence of Christ, with a conscience enlightened by the Holy Spirit.
1.      His conduct and his doctrines had led some to believe that he was an apostate, and had lost his love for his countrymen. He had forsaken their institutions, and devoted himself to the salvation of the Gentiles. He here shows them that it was not from lack of love for them.
2.      The doctrines which he was about to state and defend were of a similar character; he was about to maintain that no small part of his own countrymen, notwithstanding their privileges, would be rejected and lost. In this solemn manner, therefore, he assures them that this doctrine had not been embraced because: he did not love them, but because it was solemn, though most painful truth. He proceeds to enumerate their privileges as a people, and to show to them the strength and tenderness of his love.

Beginning with this verse we see Paul’s constant conscience pain for the unbelief of Israel, his fellow countrymen and kinsmen; a yearning in which he declares that the Holy Spirit even bears witness.  This yearning of Paul’s is so deep that he testifies that he would even be willing to be cursed to hell if it would bring about the salvation of Israel (v. 3).

“That I have great heaviness and continual sorrow in my heart.”
In this verse Paul tells us of the fact of his grief.  In the next verse he tells us the reason for his grief.

         “That I have great heaviness”

         Literally: “That my grief is great.”– That I have much grief.
.        Not so much that his countrymen are estranged from him, but that they were without the blessing of Christ. 

          HEAVINESS:  (Grk.–lupē)–Literally: “grief; sorrow; pain.”  Because the Jews were rejecting Christ their Messiah

         “and continual sorrow in my heart”
         Literally:   “And a never-ceasing pain in my heart.”

         CONTINUIAL: (Grk.–adialeiptos)–Literally: “endless; constant; never ceasing.”   This must be taken in a popular sense.  Not that he was literally all the time pressed down        with this sorrow, but that whenever he thought on this subject he had great grief; as we say     of a painful subject, it is a source of constant pain.

SORROW:  (Grk.-odunê)–pain; sorrow.”  This should have been better rendered as, “pain,” instead of “sorrow” as it is here.

         This Greek word ( odunê), signifies such sorrow as is found with women in travail; a sorrow continually affecting his heart, and afflicting his spirit, for his countrymen and kinsmen the Jews, upon the account of their obstinate infidelity, defiance of their hearts, and spirit of slumber which was fallen upon them,  Such actions had provoked God to resolve to cast them off, to reject their nation, and to scatter them up and down throughout the world.  
         A high degree of spiritual sorrow and of spiritual joy may consist together, (8:39).  By declaring his sorrow for the unbelieving Jews, who excluded themselves from all the blessings he had enumerated, he shows that what he was now about to speak; he did not speak from any prejudice to them. “That I have great grief (or, sorrow) and unceasing anguish in my heart.”  The bitter hostility of his nation to the glorious Gospel, and the awful consequences of their unbelief, weighing heavily and incessantly upon his spirit.      

“For I could wish that myself were accursed from Christ for my brethren, my kinsmen according to the flesh.”
In this verse Paul tells the reason for his grief and pain of heart.

         “For I could wish”
For I was wishing.”–This passage has been made quite controversial. 

                 WISH:  (Grk.–êuchomai)–Meaning:  “wish; long for”   “Pray;” as in II Cor. 13:7;  James 5:16.

Some have proposed to translate this as “I did wish,” as referring to a former state, when he renounced Christ, and sought to advance the interests of the nation by opposing and defying Him. But to this interpretation there are insuperable objections.
1.      The object of Paul is not to state his former feelings, but rather his present attachment to his countrymen, and willingness to suffer for them.
2.     The proper grammatical construction of the word used here is not “I did wish,” but “I could desire;” implying that he was willing now to endure it; i.e., that his present love for them was so strong that he would, if practicable, save them from the threatened ruin and apostasy.
3.     It is not true that Paul ever did wish before his conversion to be accursed by Christ, i.e. by the Messiah.  He opposed Jesus of Nazareth;  he did not believe that he was the Messiah.

         “myself were accursed from Christ”
         Literally: “To be a curse from Christ” This passage has been much controverted.

        ACCURSED:  (Grk.–anathema)-Set apart from Christ; set apart for destruction; condemned to Hell.   Subjected to the greatest calamities for his brethren, if by this means they could be saved.

“for my brethren, my kinsmen according to the flesh”
Literally:  “for my brothers, my kinsmen according to flesh.   His Jewish brethren, those of the same Jewish stock as himself. Being brethren by flesh, as from one nation and country.

Paul loved his brethren so completely that if it had been possible he would have been ready to have redeemed the castaways of the Israelites with the loss of his own soul forever: for this word "accursed" signifies as much in this place.

                 FOR:  (Grk.–huper)–For; on behalf of; for the sake of.”