Union with Christ
What is Union with Christ?
Just like God himself is three persons, yet one God, and just like a husband and wife are two people but one covenant union, the Holy Spirit unites believing sinners to Jesus by a new kind of covenant in his blood so that they, while still being separate people, are considered one with Jesus.
This special covenant explains how our sins can be paid for by his suffering. It also explains how his righteous satisfaction of all God's commands applies to us as though we had done it ourselves. It also explains how we can live with God forever and never die—by this special union, Jesus's resurrection becomes our resurrection, and his eternal, indestructible life becomes ours too.