Give a man a fish, and he'll eat for a day.
Whack him over the head with a fish, and he'll leave you alone.

On a similar note...
Change an infant's diapers, and they will be clean for an hour.
Teach an infant to change diapers, and he just may learn by the time you need them.

The first version was in a co-worker's signature file. About two years later, was married and taking some time off after his son was born. It was at this time, the signature changed to the second version.