The greatness of a nation and its moral progress can be measured by the way in which its animals are treated.
The mansahari, "meat-eater," is poignantly described in the following passage from the obscure Mansahara Parihasajalpita Stotram:
As long as human society continues to allow cows to be regularly killed in slaughterhouses, there cannot be any question of peace
A.C. Bhaktivedanta Swami Prabhupada
Refrain from killing knowingly even the trifling insects like a louse, a bug or a mosquito. Use no violence even to gain possession of a woman, wealth or kingdom. Never kill any animals even for the purpose of sacrifice. Non-violence is the greatest of all religions.
Swami Sahajanand, Divine Life Society
O lover of meditation, become pure and clean. Observe nonviolence in mind, speech and body. Never break another's heart. Avoid wounding another's feelings. Harm no one. Help all. Neither be afraid nor frighten others.
Someone who believes in violence and continues causing injury to others can never be peaceful himself.
To be free from violence is the duty of every man. No thought of revenge, hatred or ill will should arise in our minds. Injuring others gives rise to hatred.
By ahimsa, Patanjali meant the removal of the desire to kill. All forms of life have an equal right to the air of maya. The saint who uncovers the secret of creation will be in harmony with Nature's countless bewildering expressions. All men may understand this truth by overcoming the passion for destruction.
Sri Yukteswar to Paramahansa Yogananda
If you plant eggplant, you can pluck eggplants. If you sow goodness, you can reap goodness. If you sow evil, you will reap evil. Do good to all. God is there, within you. Don't kill. Don't harbor anger.
We are all of the same race and religion. We are holy beings established in Divinity itself. This truth can be understood only by those who have grasped it through the magical charm of a life of dharma-not by other means. Because of that, sages have emphatically proclaimed again and again that it is necessary to love all existing lives as one's own.
The test of ahimsa is the absence of jealousy. The man whose heart never cherishes even the thought of injury to anyone, who rejoices at the prosperity of even his greatest enemy, that man is the bhakta, he is the yogi, he is the guru of all.
Strictly speaking, no activity and no industry is possible without a certain amount of violence, no matter how little. Even the very process of living is impossible without a certain amount of violence. What we have to do is to minimize it to the greatest extent possible.
Mahatma Gandhi, My Socialism, 34-35.
You do not like to suffer yourself. How can you inflict suffering on others? Every killing is a suicide. The eternal, blissful and natural state has been smothered by this life of ignorance. In this way the present life is due to the killing of the eternal, pristine Being. Is it not a case of suicide?
Ramana Maharshi, June 1935