Why is union with Christ important for salvation?

Union with Christ is fundamental in Reformed theology, representing the believer’s relationship with Jesus through His life, death, and resurrection. This union is described in multiple ways, such as union in His blood and resurrection and signifies that all of a believer's salvation rests in what Christ has accomplished. As stated in John 17:24, Jesus desires that those given to Him 'be with me where I am,' emphasizing a deep, personal fellowship with Him, essential for spiritual life and future glorification. This union assures believers of their identity in Christ and guarantees their eternal security.