The Jews before Jesus believed that blood had redemptive powers:
all things are cleansed with blood, and without shedding of blood there is no forgiveness
To regard a substance as having such abstract powers invariably comes from a form of thinking known as sympathetic magic. JG Frazer’s The Golden Bough (1889) extensively documents and elucidates such rituals. The Jewish belief in the abstract restorative powers of blood stems from a naive essentialism that should be anathema to the modern educated mind:
In the fifties, Paul Simon and Art Garfunkel released records as that most familiar American duo, Tom & Jerry. It was the sixties before their now famous Jewish names were allowed an airing. A similar thing happened with Jesus. Truth is, without Paul, Jesus may have been simultaneously too Jewish, too old fashioned, and too radical to make it big. Jesus in the Gospels is not quite the laissez faire hippie that many Christians want him to be. He is quoted as saying
Whosoever shall put away his wife, except it be for fornication, and shall marry another, committeth adultery
yet good Christians divorce for reasons other than infidelity all the time. Society’s moral values have changed, and the moral values of Christians have changed with them. Jesus says nothing against slavery whereas a modern Christian placed in his situation and time might feel compelled to speak out.