Me neither. I was guessing that it was meant as a joke. Let me get my understanding of 'spare the rod, spoil the child' sorted out in my head.
If you 'spare' [verb] something, you cease to use it or use it far less. If you have two of the same thing, you use one of them and the other literally becomes a 'spare' [noun].
Spoiling the child must be obvious. These days if you indulge a child too much, in terms of its whims and desires, people will often say that you're 'spoiling' the kid. But back when that old phrase was coined, if you didn't beat the child with the rod/stick you were spoiling the child, whose only real desire was to be loved and not beaten. That's the Victorians for you.
Whoops, I need to explain this ...
If you don't beat your child regularly it will go bad
Spare (as in don't use it enough)
Rod (as in cane)
Spoil (as in gone bad, not treating)

