Ronald Wallace notes that the response of the believing individual to the Church is seen by Calvin as identical to responding to Christ. This is affirmed by Calvin in his Commentary on Isaiah 45:14:
When he says that the Israelites shall be victorious over all the nations, this depends on the mutual relation between the head and the members. Because the only begotten Son of God unites to Himself those who believe in Him, so that they are one with Him. It frequently happens that what belongs to Him is transferred to the Church which is His body and fulness. In this sense, rule also is attributed to the Church, not so as to obscure by haughty domination the glory of her Head, or even to claim the authority which belongs to Him, or in a word, so as to have anything separate from her Head; but because the preaching of the Gosel which is omitted to her is the spiritual scepter of Christ, by which He displays His power. In this respect no man can bow down submissively before Christ, without also obeying the Church, so far as the obedience of faith is joined to the ministry of doctrine, yet so that Christ their Head alone reigns, and alone exercises His authority.
Therefore, the ministry of the church is the ministry of Christ. When the church pronounces forgiveness of sins Christ does the same. This does not mean that the Church functions ex opere operato but that it signifies the reality of Christ’s invisible work, and God, as Calvin says in numerous places, does not deceive us with empty signs.