Christ’s fulfilment of the covenant is one of the most prominent themes in Calvin’s Hebrews commentary. However, it is hard to follow in detail if one jumps directly into the covenant theology chair passages of Hebrews 7-10. One must begin all the way back in Hebrews 3:2, which connects Calvin’s Christology and Covenant Theology using the basic grammar of promulgatio and confirmatio. This paper will lay out how Calvin understands both concepts and briefly survey how Calvin uses them in Hebrews. Promulgation is the open declaration of the revelatory content of the covenant and corresponds to Christ’s prophetic office, while confirmation is the fulfilment of the covenant by Christ’s priestly death upon the cross. Together, promulgation and confirmation make up the two parts of the covenant. The paper will then argue that this “covenantal grammar” gives the three-fold office an underappreciated covenantal rationale. They are not only redemptive offices but covenantal offices which are the only means to provide the necessary components of promulgation and confirmation. The munus triplex becomes inseparable and each office has a logical flow from one to the next as they create, regulate, and flow out of a covenant. Christ cannot simply be one office or the other but must be all three because they are linked covenantal mechanisms. Separating them from each other would compromise the coherence and integrity of God’s eternal covenant with man.