I greatly enjoyed the following video by Dr. James White, explaining to a Muslim antagonist the voluntary nature of Christ's death on the cross:
I would add that there is more revelation that declares that Jesus' sacrifice was voluntary, namely in the prophecy of that great prophet, the prophet Isaiah (prophecying of Jesus the Messiah):
7 He was oppressed, and he was afflicted, yet he opened not his mouth: he is brought as a lamb to the slaughter, and as a sheep before her shearers is dumb, so he openeth not his mouth. 8 He was taken from prison and from judgment: and who shall declare his generation? for he was cut off out of the land of the living: for the transgression of my people was he stricken.
It Jesus who was slain for the transgressions (sins) of the elect. And the prophecy continues:
9 And he made his grave with the wicked, and with the rich in his death; because he had done no violence, neither was any deceit in his mouth. 10 Yet it pleased the LORD to bruise him; he hath put him to grief: when thou shalt make his soul an offering for sin, he shall see his seed, he shall prolong his days, and the pleasure of the LORD shall prosper in his hand.
You see, Jesus was an offering for sins, by which obtained his seed - his children purchased by his blood. And still the prophecy continues:
11 He shall see of the travail of his soul, and shall be satisfied: by his knowledge shall my righteous servant justify many; for he shall bear their iniquities. 12 Therefore will I divide him a portion with the great, and he shall divide the spoil with the strong; because he hath poured out his soul unto death: and he was numbered with the transgressors; and he bare the sin of many, and made intercession for the transgressors.
It was not an easy thing to do, but He did it and was satisfied. Through his knowledge (love) many are justified, by his bearing their iniquities (sins). He poured out his soul unto death, it was his choice, and yet he is great by virtue of this humiliation.
The sins of the elect were imputed to Christ, and he bare those sins, and now makes intercession for the elect in heaven.
He is our God and our hope for eternal life. He is the fulfilment of Isaiah's prophecy.