Sukha kamani bhutani yo dandena vihimsati
Attano sukham esano pecca so na labhate sukham.
He who seeks his own happiness by harming others who also desire to have happiness will not find happiness hereafter. 
Sukha kamani bhutani yo dandena na himsati
Attano sukham esano pecca so labhate sukham.
He who seeks his own happiness by not harming others who also desire to have happiness will find happiness hereafter. 
Once, the Buddha was out on an almsround at Savatthi, when he came across a number of youths beating a snake with sticks. When questioned, the youths answered that they were beating the snake because they were afraid that the snake might bite them.
The Buddha admonished them, 'If you don't want to be harmed, you should also not harm others*: if you harm others, you will not find happiness even in your future existence.'
Perceiving the evils of hatred and reflecting mindfully on the admonition of the Enlightened One, all the youths attained the first stage of Sainthood.
*A genuine Buddhist should practisemetta(loving kindness) towards every living being and should identify himself with all, making no distinctions whatsoever.