Spare the Rod, oh wait...
Matthew 18:6 [ Causing to Stumble ] “If anyone causes one of these little ones—those who believe in me—to stumble, it would be better for them to have a large millstone hung around their neck and to be drowned in the depths of the sea.
Mark 9:42 [ Causing to Stumble ] “If anyone causes one of these little ones—those who believe in me—to stumble, it would be better for them if a large millstone were hung around their neck and they were thrown into the sea.
Luke 17:2 It would be better for them to be thrown into the sea with a millstone tied around their neck than to cause one of these little ones to stumble.
https://www.biblegateway.com/quicksearch/?quicksearch=millstone&qs_version=NIV