John Gill expounds on Christ as the Testator of the Covenant, emphasizing that the covenant of grace is akin to a testament, established by God's sovereign will and not by obligation. He illustrates that Christ, as both the testator and executor, has the authority to dispense blessings to His people, which are secured through His death. The sermon highlights the eternal nature of this covenant, its unalterable promises, and the significance of Christ's sacrifice in validating the testament. Gill also notes that the Holy Spirit serves as a witness to this covenant, ensuring believers' assurance of their inheritance. Ultimately, the covenant is a testament of grace, freely given to the elect without any merit on their part.