If a Christian said to me that the Christian’s inheritance was eternal life in heaven, I would not argue with his statement. But, to my mind, eternal life in heaven is actually a side benefit of the Christian’s inheritance.
The natural inheritance of all human beings is explained briefly and succinctly in the counsel given to ministers: “Tell the people in clear, hopeful language how they may escape the heritage of shame which is our deserved portion.” Selected Messages, Book 1, 182
If you look up the word heritage in the dictionary, you will see that it is something inherited, a birthright. The dictionary definition of the word shame is a strong negative emotion caused by guilt or a painful sense of guilt and unworthiness.
So, our natural inheritance is guilt. This is our deserved portion, and therefore, our natural destination is everlasting death. When Adam sinned, there was only one Person in the universe who could save the human race from everlasting death. Salvation involves an exchange. Jesus, the second person of the Godhead, came to this world and took our inheritance of guilt, shame, and death upon Himself. He took our place and bore our punishment, while offering to us His place, His inheritance.
What was Jesus’ inheritance when He came to this world? He did not have a human father, so He did not inherit from Adam what we inherited from him. God was His Father. Jesus, even as a man, inherited from His Father perfect everlasting righteousness, and this inheritance He offers to you and me. If we have the faith of Abraham, we will inherit, by adoption, the inheritance of Christ, and will no longer be children of the devil (see Ephesians 2:3, 1 John 3:8). Having been born again, we become the children of the Most High and joint heirs with Jesus Christ to an everlasting kingdom. If Adam had not sinned, he would have given to us—his posterity—an inheritance of purity and perfection. “If faithful to God’s requirements, he [Adam] would have had perfect descendants, as pure and uncorrupted as he himself was when he came from the hand of God. … But by his disobedience he spoiled God’s plan for himself and for his posterity.” The Review and Herald, December 15, 1896
The only way that we can receive purity and righteousness is through the second Adam, Jesus Christ.