What does the mystery of Christ refer to?

The mystery of Christ, as mentioned in Colossians 1:26, refers to the gospel that unveils God's plan of salvation, through Jesus Christ, to both Jews and Gentiles. This gospel was previously hidden but has now been made manifest to His saints, demonstrating God's sovereign grace in choosing a people for Himself. It encompasses the work of Christ in redeeming His people, fulfilling the law, and offering salvation through faith alone. Recognizing this mystery helps Christians appreciate the depth of God's love and purpose in their salvation and motivates them to share this truth with others.