The inheritance we receive is the everlasting kingdom of Christ.
Paul, an apostle of Jesus Christ through the will of God, to the saints who are in Ephesus, and to the faithful in Christ Jesus: (Eph. 1:1, YLT)
Paul wrote this letter to the assembly of the saints in Ephesus while he was in prison in about 61-62 AD.1 The Ephesians were living in the first century AD and were those who having believed the command to be immersed into Christ (Eph. 1:13) were sealed (anointed) by the Holy Spirit, and became fellow heirs in Christ.
Heirs inherit wealth and property at the death of their parents or other family members according to a will that lists specific items or benefits and is a legal promise recognized by the courts of men. God’s promise to Abraham is the promise/blessing (or legal will) spoken of in the letters of the New Testament and given by His oath.
and if ye [are] of Christ then of Abraham ye are seed, and according to promise--heirs. (Gal. 3:29, YLT)
The promise is that which God gave to Abraham in Gen. 12:1-7 that all nations would be blessed through the promised son; that through Isaac would God raise up a savior for His people, the children of Abraham, Isaac, and Jacob. The promise involved blessings to Abraham himself, and to his offspring, as well as a promise of a land to live in (Gen. 12:7), and to bless all nations through Abraham.
”23 'Of this one's seed God, according to promise, did raise to Israel a Saviour--Jesus,… 32 And we to you do proclaim good news--that the promise made unto the fathers, 33 God hath in full completed this to us their children, having raised up Jesus,… 38 'Let it therefore be known to you, men, brethren, that through this one to you is the forgiveness of sins declared, 39 and from all things from which ye were not able in the law of Moses to be declared righteous, in this one every one who is believing is declared righteous;” (Acts 13:23, 32-33,38-39, YLT)
God told us that the earthly land promise had been completely fulfilled (Josh. 21:45). The land promise was conditional upon their obedience to His statutes and laws (Deu. 7; 20:17). God gave the Israelites a bill of divorcement because of their spiritual adultery in following after idols (Isa. 50:1; Jer. 3:8; Exek. 36:17-19). Their disobedience nullified the earthly land promise. But, the rest of the blessings promised to Abraham for righteousness, forgiveness of sins, and salvation were still to come.
13 For to Abraham God, having made promise, seeing He was able to swear by no greater, did swear by Himself, 14 saying, 'Blessing indeed I will bless thee, and multiplying I will multiply thee;'
15 and so, having patiently endured, he did obtain the promise; 16 for men indeed do swear by the greater, and an end of all controversy to them for confirmation [is] the oath,
17 in which God, more abundantly willing to shew to the heirs of the promise the immutability of his counsel, did interpose by an oath, (Heb. 6:13-17, YLT)
8 By faith Abraham, being called, did obey, to go forth to the place that he was about to receive for an inheritance, and he went forth, not knowing whither he doth go; 9 by faith he did sojourn in the land of the promise as a strange country, in tabernacles having dwelt with Isaac and Jacob, fellow-heirs of the same promise, (Heb. 13:8-9, YLT)
5 which in other generations was not made known to the sons of men, as it was now revealed to His holy apostles and prophets in the Spirit--6 that the nations be fellow-heirs, and of the same body, and partakers of His promise in the Christ, through the good news, (Eph. 3:5-6, YLT)
Hearken, my brethren beloved, did not God choose the poor of this world, rich in faith, and heirs of the reign that He promised to those loving Him? (James 2:5, YLT)
What reign do the heirs of Abraham now receive? It is not a bounded land-based nation. It is now a spiritual kingdom (Luke 17:21), the new spiritual promised land of the spiritual nation of Christ’s everlasting kingdom. 2)
And saying, Repent ye: for the kingdom of heaven is at hand. (Matt. 3:5, KJV)
From that time Jesus began to preach, and to say, Repent: for the kingdom of heaven is at hand. (Matt. 4:17, KJV)
Blessed are the poor in spirit: for theirs is the kingdom of heaven. (Matt. 5:3, KJV)
But seek ye first the kingdom of God, and his righteousness; and all these things shall be added unto you. (Matt. 6:33, KJV)
And I say unto you, That many shall come from the east and west, and shall sit down with Abraham, and Isaac, and Jacob, in the kingdom of heaven. (Matt. 8:11, KJV)
And as ye go, preach, saying, The kingdom of heaven is at hand. (Matt. 10:7, KJV)
The kingdom of heaven is the new promised land. It was legally established at the death of Christ in about 30-31 AD, but the will/promise had to be legally probated, the will had to be read throughout the lands (Matt. 24:14) and the conditions met before the kingdom would be fully established in that generation (Matt. 5:18; 24:34).
Christ told those who heard Him speak in the first century AD that the kingdom was coming but was not yet with them.
Verily I say unto you, There be some standing here, which shall not taste of death, till they see the Son of man coming in his kingdom. (Matt. 16:28, KJV)
So, some of those standing there with Christ in about 30 AD would still be living when Christ returned to completely establish His kingdom. In the prophecy of the destruction of the temple, the Olivet Discourse, Jesus told them when His kingdom would come.
Heaven and earth shall pass away, but my words shall not pass away. (Matt. 24:35. KJV)
Heaven and earth was the phrase the Jews used for the temple. It was also the phrase God used for the Mosaic Covenant (Deu. 4:26; 31:26). At His return, the will would have been probated and preached throughout the nations (Rom. 15:19; Col. 1:23)), all the word of the old Roman empire, and only then would that earthly temple fall, and that old Mosaic covenant would pass away (Heb., 8:13). The kingdom was fully established in AD 70 when that earthly temple fell.
So, the promise of the inheritance into the kingdom was still ahead of those saints living during the days of Christ’s ministry, and during the days the Apostles and disciples were teaching the gospel news in the first century AD. The gift of the Holy Spirit was their down payment or earnest money, or escrow for the fulfilled payment/blessing of the coming inheritance they were promised to receive when the kingdom was fully set in place.
The benefits of the inheritance of Christ’s everlasting kingdom were and still are forgiveness of sins (2 Cor. 5:19), being clothed in Christ’s righteousness (Isa. 61:10; 2 Cor. 5:21), immortality (1 Cor. 15:53) eternal salvation (Heb. 5:9), and eternal life with our Father in heaven (John 3:15)
Today, we who have been immersed into Christ are counted for the seed of Abraham (Gal. 3:26-29), are clothed with Christ’s righteousness when we rise up that new creature (2 Cor. 5:17), our names are written into the book of life (Phil. 4:3) and we are entered into Christ's everlasting kingdom. If we remain faithful unto death (Rev. 14:13), we will receive the full blessings of our inheritance when we enter into heaven itself.
Notes:
Dating the New Testament: The Letter to the Ephesians
The Promised Land: Between the Cross and the Kingdom