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general::
Discipline is necessary for good upbringing, as in She lets Richard get away with anything? spare the rod, you know. This adage appears in the Bible (Proverbs 13:24) and made its way into practically every proverb collection. It originally referred to corporal punishment. It is still quoted, often in shortened form, and today does not necessarily mean physical discipline.
American Heritage Idioms
2
general::
Phrase(s): Spare the rod and spoil the child.
Prov. You should punish a child when he or she misbehaves, because if you do not, the child will grow up expecting everyone to indulge him or her. • Jane: How can you allow your little boy to be so rude? Ellen: It distresses me to punish him. Jane: I can understand that, but spare the rod and spoil the child.
McGrawhill's American Idioms And Phrasal Verbs