bible verse
“And if anyone causes one of these little ones who believe in me to sin, it would be better for him to be thrown into the sea with a large millstone tied around his neck.”
meaning
A millstone around your neck is a problem or responsibility that prevents you from doing what you want to do.
origin and application
Jesus warned that those who persuaded Christians, be them the weakest, to sin would be severely punished. It would be better for them that a millstone were hanged around their neck, and thrown into the sea.
example
His credit card debt has become a millstone round his neck.