What does it mean that believers are joint heirs with Christ?

Being joint heirs with Christ means that everything belonging to Christ becomes the rightful property of the believer. This was the mystery revealed for Gentiles in the Body of Christ: Gentiles would become fellow heirs with Him, a promise Israel never received.

Les explains that the mystery amounts to this: the Gentiles were of all things going to become fellow heirs with Christ. Israel never had a promise like that; Israel never had a promise that they would be joint heirs with Christ. Using a legal illustration, Les asks what this means, and the idea given is that what belongs to one belongs to everybody. Therefore everything that is Christ is now going to be the rightful property of the believer, as Gentiles are joint heirs in the Body of Christ.

What does it mean for believers to be heirs of God and joint heirs with Christ?

Scripture teaches that at salvation, through the Spirit of Adoption, God declares believers full children and heirs. Being heirs of God and joint heirs with Christ means believers are co-equal with Him in inheritance: everything that is Christ’s will one day be theirs.