Victorinus of Poetovio
"I saw," he says, "an angel proclaiming with a loud voice: Who is worthy to open the book and loose its seals?
And no one was found worthy, either in heaven or on earth or under the earth."
To open the covenant means to suffer for men and finally conquer death.
No one was found worthy to do this: neither among the angels in heaven, nor among men on earth, nor among the souls of the saints abiding in rest.
Only Christ, the Son of God, was worthy. Of Him he says: "I saw a Lamb as though slain, having seven horns" (Rev 5:6).
It had been foretold of Him that whatever law had been devised concerning Him through various gifts and sacrifices, He Himself had to fulfill it.
Because He Himself was the Testator and conquered death, He Himself was found appointed by God as the lawful heir.
Thus He was to possess also the substance of mortal being, that is, the human body.
This means that Jesus Christ is the Testator, or Mediator, of the New Testament. See Heb 8:6.