B'resheet 25:31-34 But Ya'akov said, "First sell me your birthright." And Esav said, "Behold, I am about to die; so of what use then is the birthright to me?" And Ya'akov said, "First swear to me"; so he swore to him, and sold his birthright to Ya'akov. Then Ya'akov gave Esav bread and lentil stew; and he ate and drank, and rose and went on his way. Thus Esav despised his birthright. NAS
The birthright - a double portion of the inheritance was given to the first-born.
D'varim (Deuteronomy) 21:16-17 But he shall acknowledge the first-born, the son of the unloved, by giving him a double portion of all that he has, for he is the beginning of his strength; to him belongs the right of the first-born.
Also the first-born had the right to be the family chief and priest.
Hebrews 12:14-17 Pursue peace with all men, and the sanctification without which no one will see the L-rd. See to it that no one comes short of the mercy/grace of G-d; that no root of bitterness springing up causes trouble, and by it many be defiled; that there be no immoral or godless person like Esav, who sold his own birthright for a single meal. For you know that even afterwards, when he desired to inherit the blessing, he was rejected, for he found no place for repentance, though he sought for it with tears. NAS
Esav had a responsibility as the first-born son but despised it and by doing so turned his back on the Almighty. The Almighty chose Ya'akov to receive the better blessing. Why?
It had nothing to do with what Esav did or what Ya'akov did. HaShem will have mercy on whom He will have mercy!
Israel is G-d's first-born.
Exodus 4:22-23 Then you shall say to Pharaoh, 'Thus says the L-RD," Israel is My son, My first-born.
Israel as a nation was given the responsibility of the Law and the adoption as the children of the Most High, yet they "as a nation" missed the better blessing and largest portion of the blessing and the responsibility was eventually given to all nations. Yet "as a nation"-not any nation has totally come to Yeshua as their Messiah.
Paul a Hebrew grieves deeply along with Ruach HaKodesh. Paul would have rather he be accursed and separated from Messiah for the sake of some of his brothers that would not come to their true and only true Messiah. In other word's He was willing be separated from our Messiah if only his brothers would come to know the love of Yeshua and G-d's only Son. This is how much he loved them. This is how much Ruach HaKodesh loves them. This is how much the Son loves them. He separated Himself from the Father, from the glory of heaven, to die and rise again for those that trust in the word from the Father.
Romans 9:1-5 I am telling the truth in Messiah (Christ), I am not lying, my conscience bearing me witness in Ruach Ha Kodesh (the Holy Spirit), that I have great sorrow and unceasing grief in my heart. For I could wish that I myself were accursed, separated from Messiah (Christ) for the sake of my brethren, my kinsmen according to the flesh, who are Israelites, to whom belongs the adoption as sons and the glory and the covenants and the giving of the Law and the temple service and the promises, whose are the fathers, and from whom is the Messiah (Christ) according to the flesh, who is over all, G-d blessed forever. Amen.
The greater blessing would go to Israel first then pass on to all nations. Why?
Romans 9:6-26 But it is not as though the word of G-d has failed. For they are not all Israel who are descended from Israel; neither are they all children because they are Avraham's descendants, but: "through Yitz'chak your descendants will be named." That is, it is not the children of the flesh who are children of G-d, but the children of the promise are regarded as descendants. For this is a word of promise: "At this time I will come, and Sarah shall have a son." And not only this, but there was Rivkah also, when she had conceived twins by one man, our father Yitz'chak; for though the twins were NOT YET BORN, and had NOT DONE ANYTHING GOOD OR BAD, in order that G-d's purpose according to His choice might stand, not because of works, but because of Him who calls, it was said to her, "The older will serve the younger." Just as it is written, "Ya'akov I loved, but Esav I hated." What shall we say then? There is no injustice with G-d, is there? May it never be! For He says to Moses, "I will have mercy on whom I have mercy, and I will have compassion on whom I have compassion." So then it does not depend on the man who wills or the man who runs, but on G-d who has mercy. For the Scripture says to Pharaoh, "For this very purpose I raised you up, to demonstrate My power in you, and that My name might be proclaimed throughout the whole earth." So then He has mercy on whom He desires, and He hardens whom He desires. You will say to me then, "Why does He still find fault? For who resists His will?" On the contrary, who are you, O man, who answers back to G-d? The thing molded will not say to the molder, "Why did you make me like this," will it? Or does not the potter have a right over the clay, to make from the same lump one vessel for honorable use, and another for common use? What if G-d, although willing to demonstrate His wrath and to make His power known, endured with much patience vessels of wrath prepared for destruction? And He did so in order that He might make known the riches of His glory upon vessels of mercy, which He prepared beforehand for glory, even us, whom He also called, not from among Jews only, but also from among Gentiles. As He says also in Hosea,"I will call those who were not My people, 'My people,' And her who was not beloved, 'beloved.'" "And it shall be that in the place where it was said to them, ' you are not My people,' There they shall be called sons of the living G-d." NAS
Isaiah 10:22 Isaiah cries out concerning Israel, "Though the number of the sons of Israel be as the sand of the sea, it is the remnant that will be saved; for the L-rd will execute His word upon the earth, thoroughly and quickly. "