Oath and Covenant
Oaths were once basic to society. No covenant could be made without curses. Every time a covenant was made you invoked curses upon yourself for disobedience. If two men made a covenant together they would say may such and such a thing happen to me if I am faithless to this covenant. And when man made a covenant with God either God pronounced it and they said amen to it or they themselves were required to say it.