"The Ariyan disciple thus reflects, Here am I, fond of my life, not wanting to die, fond of pleasure and averse from pain. Suppose someone should rob me of my life... it would not be a thing pleasing and delightful to me. If I, in my turn, should rob of his life one fond of his life, not wanting to die, one fond of pleasure and averse from pain, it would not be a thing pleasing or delightful to him. For a state that is not pleasant or delightful to me must also be to him also; and a state that is not pleasing or delightful to me, how could I inflict that upon another? As a result of such reflection he himself abstains from taking the life of creatures and he encourages others so to abstain, and speaks in praise of so abstaining."
Samyutta Nikaya v.353
"One should seek for others the happiness one desires for himself."
"Is there a deed, Rahula, thou dost wish to do? Then bethink thee thus: Is this deed conducive to my own harm, or to others harm, or to that of both? Then is this a bad deed entailing suffering. Such a deed must thou surely not do."