That the Gentiles should be fellow-heirs - Fellow-heirs with the ancient people of God - the Jews - and entitled to the same privileges; see the Romans 8:17, note and Ephesians 2:13-18, note.

That the Gentiles should be fellow heirs - This is the substance of that mystery which had been hidden from all ages, and which was now made known to the New Testament apostles and prophets, and more particularly to St. Paul.
His promise in Christ - That the promise made to Abraham extended to the Gentiles, the apostle has largely proved in his Epistle to the Romans; and that it was to be fulfilled to them by and through Christ, he proves there also; and particularly in his Epistle to the Galatians, see Galatians 3:14. And that these blessings were to be announced in the preaching of the Gospel, and received on believing it, he every where declares, but more especially in this epistle.

That the Gentiles should be fellowheirs,.... With the Jews, of all the blessings of grace, of lasting salvation, and of the eternal, incorruptible, and never fading inheritance in heaven; that they should be heirs of God, and joint heirs with Christ Jesus, and inherit all things: and heirs they are by being Christ's, and on account of their special adoption through him, and their justification by his righteousness; and which appears by their regeneration to a lively hope of the inheritance reserved for them in heaven:
and of the same body: coalesce in one and the same church state, with the believing Jews, under one and the same head, Christ Jesus, and participate of the same grace from him, being all baptized into one body, and made to drink of the same Spirit, and enjoy the same privileges and immunities.
And partakers of his promise in Christ by the Gospel; as of God, being their covenant God, which is the great promise of the covenant; or of the Spirit, his gifts and graces, called the promise of the Spirit; or of eternal life and happiness, as the gift of grace through Christ. Now all these promises, and all others, are in Christ, yea and amen, safe and secure; and it is through being in Christ that any come to partake of them; and that by the means of the Gospel, as these Gentiles were to do, and did: the Gospel is a declaration of what God has promised in covenant to his people; this was carried among the Gentiles, and was made effectual to their participation of the things contained in it.

Translate, "That the Gentiles are," &c. "and fellow members of the same body, and fellow partakers of the (so the oldest manuscripts read, not 'HIS') promise, in Christ Jesus (added in the oldest manuscripts), through the Gospel." It is "in Christ Jesus" that they are made "fellow heirs" in the inheritance of GOD: "of the same body" under the Head, CHRIST JESUS; and "fellow partakers of the promise" in the communion of THE HOLY SPIRIT (Ephesians 1:13; Hebrews 6:4). The Trinity is thus alluded to, as often elsewhere in this Epistle (Ephesians 2:19-20, Ephesians 2:22).

That the gentiles are joint - heirs - Of God. And of the same body - Under Christ the head. And joint - partakers of his promise - The communion of the Holy Ghost.