WHO IS ISRAEL?
We see in the Old Testament that Israel in the flesh suffered time after time after time because they violated the Law that Yahweh gave them and worshipped other gods and finally they as a nation were destroyed and carried off into captivity and dispersed throughout the known world.
And who are heirs to the kingdom of God?
The ones we call Jews today are the remnant left from what was the southern tribes, Judah, Levi and Benjamin.
Romans 3 Now we know that what things soever the law saith, it saith to them who are under the law: that every mouth may be stopped, and all the world may become guilty before God. Therefore by the deeds of the law there shall no flesh be justified in his sight: for by the law is the knowledge of sin.
Romans 8 For what the law could not do, in that it was weak through the flesh, God sending his own Son in the likeness of sinful flesh, and for sin, condemned sin in the flesh:
God knew Israel could never obey the law, they were used as an example for us.
Galatians 2: I do not frustrate the grace of God: for if righteousness come by the law, then Christ is dead in vain.
Galatians 3 But before faith came, we were kept under the law, shut up unto the faith which should afterwards be revealed.
 Wherefore the law was our schoolmaster to bring us unto Christ, that we might be justified by faith.
Israel rejected their Messiah and had him nailed to the cross. Jesus gave the parable of the vineyard in Matthew21:33 that ended with the husbandman killing the owners son to obtain the inheritance.So Jesus says in Matthew 21:43 Therefore say I unto you, The kingdom of God shall be taken from you, and given to a nation bringing forth the fruits thereof.
Romans 9: Not as though the word of God hath taken none effect. For they are not all Israel, which are of Israel:
 Neither, because they are the seed of Abraham, are they all children: but, In Isaac shall thy seed be called.
 That is, They which are the children of the flesh, these are not the children of God: but the children of the promise are counted for the seed.
LET ME PUT THAT ONE MORE TIME , They which are the children of the flesh, these are not the children of God:
Galatians 3: There is neither Jew nor Greek, there is neither bond nor free, there is neither male nor female: for ye are all one in Christ Jesus.
 And if ye be Christ's, then are ye Abraham's seed, and heirs according to the promise.