"The Israelites became partakers of the promise as a holy people. Yet together with them the Gentiles also shared in it, though until then they had been unclean. The Apostle was not content to say that they too became fellow heirs and fellow partakers. Wishing to show their still greater closeness and unity, he said that they are of the same body. For the Gentiles, together with holy Israel, became one body, ordered and sustained by one Head, Christ" (Theophylact).
One need not inquire with precision what each of these words especially means: fellow heirs, of the same body, fellow partakers. They all signify one thing: the utter drawing together of Jews and Gentiles in the Kingdom of Christ, where every difference between them disappears.
Whichever side of the former advantage of the Jews you take, it now also belongs to the Gentiles. They did not receive it separately, but together with the Jews. Blessed Theodoret explains why some of these words were used: "Since he called the faithful one body, he says that the Gentiles became of the same body. Since the inheritance was considered to belong to the Jews, he also called the Gentiles fellow heirs. Since the Jews thought that the promises had been given to them alone, of which the Apostle also said in Romans, 'to whom belong the promises' (Rom 9:4), he likewise called the Gentiles fellow partakers of the promise."
Chrysostom does not explain why this or that word was used. He gives them all one meaning: the close union of Jews and Gentiles. "What does it mean to be fellow heirs, fellow partakers of the promise, and of the same body? The meaning of these words is lofty. They signify that the Gentiles and Jews are joined into one body. They signify their close union. That the Gentiles would be called was known before. But to what exactly they would be called, no one had known until then. For this reason the Apostle calls it the mystery of God's promise. The Israelites had been partakers of the promise before. Now the Gentiles too have been made fellow partakers of this promise."
Yet one may also see certain particular meanings in each of these words. Thus one may think that fellow heirs signifies the reception of what was anciently promised to Israel as an inheritance. Of the same body signifies what has newly been received in the gracious Kingdom of Christ. Fellow partakers of the promise signifies what is to be received by all in the future.
Here is depicted the ladder of blessings flowing from the person of Jesus Christ upon our race. The blessings of the Old Testament, both those received then and those promised to future generations, are the first step. The blessings received from the Lord after His Incarnation in His Holy Church, in the present period until the Second Coming, are the second step. What is promised in the age to come, and will be received after the restoration of all things, is the third and ineffable step.
The Apostle wishes to say to the Gentiles: you have been deprived of nothing. What was promised to Israel you have received together with Israel. What beyond that promise has been given to faith is granted to you according to faith. What has been prepared in the future will also be yours.
All this is the wondrous mystery which no one could comprehend. It barely found room in the minds of the chosen Apostles, and that only through a special action from without and inward working of the Most Holy Spirit. See what you have been counted worthy to receive. Therefore remember.
"In Christ Jesus through the gospel." To such a height you have been raised. Such blessings you have been granted. Thus you have come together with Israel in Christ Jesus, through faith in Him and through the grace of the Holy Spirit received for faith. This grace recreates all and makes all alike.
You were drawn into participation in this through the gospel, for faith comes by hearing. "The Gentiles shared in the promise through the fact that evangelists were sent to them, and they believed them. They did not simply become fellow partakers of the promise, but did so through the gospel" (Chrysostom). "Through faith in Christ they became fellow partakers, but faith came to them through the gospel" (Theophylact).
Yet the whole force is directed to this: therefore remember. For the gospel would not have come by itself. Evangelists had to be chosen and formed. They had to be equipped with every power and sent to preach the gospel, while being guided and aided in every way in this preaching.
The Israelites had all this at home. But to you someone had to be deliberately sent to such a distance. Hinting at this, the Apostle says:
THEOSIS