You don't punish a fish by throwing it into water.
If you are to punish someone, the action you prescribe for them as punitive should not be a positive reinforcement. The punishment must in someway sting the person, otherwise the person would not learn from their mistakes.
This proverb is applicable to unjust politicians, for example, who would reward members of their cabinet they like even when those members fail to perform well.
Note: This interpretation is our opinion. We encourage you to agree, disagree, or provide an alternate interpretation.