'Backs' in the Bible

Nevertheless they were disobedient, and rebelled against thee, and cast thy law behind their backs, and slew thy prophets which testified against them to turn them to thee, and they wrought great provocations.

and testified against them, that you might bring them again to your law. Yet they dealt proudly, and didn't listen to your commandments, but sinned against your ordinances, (which if a man does, he shall live in them), turned their backs, stiffened their neck, and would not hear.