The Catechism in Questions & Answers

247. What is the foundation for salvation?

Jesus Christ is the author of eternal salvation: “And having been perfected, He became the author of eternal salvation to all who obey Him” (Hebrews 5: 9). He is the only Mediator between God and man (cf. 1 Timothy 2: 5). Acts 4: 12 attests: “Nor is there salvation in any other, for there is no other name under heaven given among men by which we must be saved.”
Jesus Christ is the Saviour sent by God. He is the Redeemer who has conquered sin. In Him human beings find salvation from the harm caused by sin: the sacrifice that Jesus brought on the cross makes liberation from sin—and the undoing of permanent separation from God—possible.

“Mediator”: On the one hand Jesus Christ is a “Mediator” in the sense that He mediates between God and mankind. This means that He represents mankind before God, and God before mankind. He is the Advocate of mankind before God, and acquaints human beings with the divine will. On the other hand, as “Mediator” He is also the way of salvation that leads back into fellowship with God.

“For there is one God and one Mediator between God and men, the Man Christ Jesus, who gave Himself a ransom for all.”
1 Timothy 2: 5, 6