How do we justify a moral code?

From Karen Armstrong’s A History of God: The 4,000-Year Quest of Judaism, Christianity and Islam:

God created adam, a single man, to teach us that whoever destroyed a single human life would be punished as though he had destroyed the whole world; similarly to save a life was to redeem the whole world.  This was not just a lofty sentiment but a basic legal principle….  To humiliate anybody … was one of the most serious offenses, because it was equivalent to murder, a sacrilegious denial of God’s image.  The right to liberty was crucial: it is difficult to find a single reference to imprisonment in the whole of rabbinic literature, because only God can curtail the freedom of a human being. … Jews were not to think of a God as a Big Brother, watching their every move from above; instead they were to cultivate a sense of God within each human being so that our dealings with others became sacred encounters.