Enishi, Being washed clean in the blood actually goes back to the ancient worship of childbirth. Before the patriarchal gods nature was like a god, procreation was divine. And there was a fear of women who could bleed and not die. Many men began rites of bleeding to immitate womens mentrual cycles which used to coinside with the lunar cycles. Barbara Walker has written some about this, some others too.
In ancient religions women and snakes represented wisdom. You can see why the bronze age god of war wouldn't like that, even in Egypt the god's wife was always in the house of Pharoah. In fact, women had previously been the king makers. Oh gosh so much to read but worth every second.
BTW welcome, Panda