Anselm’s Cur Deus Homo, part 11.
For Anselm, then, Christ’s suffering and death were not commanded by God, but this does not mean that they were not willed by him. As has been said previously, because of his perfect obedience as a human being, there was nothing in Christ’s specifically human nature that required his sacrificial death for the human race, yet the latter was nevertheless something which Christ willed to undertake as an act that went “above and beyond,” as it were, his mere human obedience. And like all proper acts of will, Christ’s will to suffer and to die came from God. God gave Christ the will to suffer and to die, in other words, not in satisfaction of his created human nature per se (for his human nature needed no such will for its perfection or completion), but simply as an act of Christ’s free will unnecessitated or uncompelled by his or any other created nature. The resulting paradox is that only as a free, uncoerced choice, absent of all moral duty or divine command, could Christ’s suffering and death be (as Anselm shall explain more fully later) a sufficient or suitable repayment of humankind’s debt of sin, and so fulfill God’s own uncommanded wish that the human race should be saved.