When the Creator tells you to do something like that, you want to get it in writing just in case the judge has a different theological take on the matter.
After these things God tested Abraham and said to him, “Abraham!” And he said, “Here I am.” He said, “Take your son, your only son Isaac, whom you love, and go to the land of Moriah, and offer him there as a burnt offering on one of the mountains of which I shall tell you.”
--Genesis 22:1-2
Blind obedience to god telling you to murder someone, no matter how dear they are to you, is one of the most highly praised actions in the Abrahamic canon.