It is forbidden to tie the legs of a beast or of a bird in a manner as to cause them pain. - The Code of Jewish Law

It is forbidden, according to the law of the Torah, to inflict pain upon any living creature. On the contrary, it is our duty to relieve the pain of any creature, even if it is ownerless or belongs to a non-Jew. - The Code of Jewish Law

When horses, drawing a cart, come to a rough road or a steep hill, and it is hard for them to draw the cart without help, it is our duty to help them, even when they belong to a non-Jew, because of the precept not to be cruel to animals, lest the owner smite them to force them to draw more than their strength permits. - The Code of Jewish Law

The current treatment of animals in the livestock trade definitely renders the consumption of meat as halachically unacceptable as the product of illegitimate means...As it is halachically prohibited to harm oneself and as healthy, nutritious vegetarian alternatives are easily available, meat consumption has become halachically unjustifiable. - Rabbi David Rosen, Vegetarianism: An Orthodox Jewish Perspective

It seems doubtful from all that has been said whether the Torah would sanction "factory farming," which treats animals as machines, with apparent insensitivity to their natural needs and instincts. This is a matter for decision by halachic authorities. - Rabbi Aryeh Carmell, Masterplan: Judaism: its Programs, Meanings, Goals (1991).

And the flesh of the slain beasts in his body will become his own tomb. For I tell you truly, he who kills, kills himself and he who eats the flesh of slain beasts, eats the body of death. - The Essene Gospel of Peace

A righteous man cares for the needs of his animal. - Proverbs 12:10, Mathew 25:40

The tzaddik (righteous person) acts according to the laws of justice; not only does he act according to these laws with human beings, but also with animals. - Rabbi Meir Leibush ben Yechiel Michel, chief Rabbi of Romania

Auschwitz begins wherever someone looks at a slaughterhouse and thinks: they're only animals. - Theodor Adorno, German Jewish philosopher

We cannot treat any living thing callously, and we are responsible for what happens to other beings, human or animal, even if we do not personally come into contact with them. - Rabbi Pinchas Peli, Prof. of Jewish Thought, Ben-Gurian Univ., Israel

Apparently the Torah was in principle opposed to the eating of meat. When Noah and his descendants were permitted to eat meat this was a concession conditional on the prohibition of the blood. This prohibition implied respect for the principle of life ("for the blood is the life") and an allusion to the fact that in reality all meat should have been prohibited. This partial prohibition was designed to call to mind the previously total one. - Rabbi Moses Cassuto

Here you are faced with God's teaching, which obliges you not only to refrain from inflicting unnecessary pain on any animal, but to help and, when you can, to lessen the pain whenever you see an animal suffering, even through no fault of yours. As God is merciful, so you also be merciful. As he loves and cares for all His creatures and His children and are related to Him, because He is their Father, so you also love all His creatures as your brethren. Let their joys be your joys, and their sorrows yours. Love them and with every power which God gives you, work for their welfare and benefit, because they are the children of your God, because they are your brothers and sisters. - Rabbi Samson Rafael Hirsch, father of German Jewish orthodoxy, Chief Rabbi of Austria, Horeb, Chapter 72, Section 482

It appears that the first intention of the Maker was to have men live on a strictly vegetarian diet. The very earliest periods of Jewish history are marked with humanitarian conduct towards the lower animal kingdom...It is clearly established that the ancient Hebrews knew and perhaps were the first among men to know, that animals feel and suffer pain. - Rabbi Simon Glazer

Jews will move increasingly to vegetarianism out of their own deepening knowledge of what their tradition commands...Man's carnivorous nature is not taken for granted or praised in the fundamental teachings of Judaism...A whole galaxy of central rabbinic and spiritual leaders...has been affirming vegetarianism as the ultimate meaning of Jewish moral teaching. - Rabbi Isaac ha-Levi Herzog

There are probably no creatures that require more the protective Divine word against the presumption of man than the animals, which like man have sensations and instincts, but whose body and powers are nevertheless subservient to man. In relation to them man so easily forgets that injured animal muscle twitches just like human muscle, that the maltreated nerves of an animal sicken like human nerves, that the animal being is just as sensitive to cuts, blows, and beating as man. Thus man becomes the torturer of the animal soul. - Rabbi Samson Rafael Hirsch, father of German Jewish orthodoxy, Chief Rabbi of Austria, Horeb, Chapter 60, Section 415

We are instructed by the Torah to feed our animals before we feed ourselves. - Herb Newman

You are permitted to use the animals and employ them for work, have dominion over them in order to utilize their services for your subsistence, but must not hold their life cheap nor slaughter them for food. Your natural diet is vegetarian. - Rabbi Moses Cassuto

Living creatures possess a moving soul and a certain spiritual superiority which in this respect make them similar to those who possess intellect (people) and they have the power of affecting their welfare and their food and they flee from pain and death. - Rabbi Nachmanides, Philosopher, Physician, Kabalah scholar, mystic

It should not be believed that all beings exist for the sake of the existence of man. On the contrary, all the other beings too have been intended for their own sakes and not for the sake of anything else...there is no difference between the pain of humans and the pain of other living beings, since the love and tenderness of the mother for the young are not produced by reasoning, but by feeling, and this faculty exists not only in humans but in most living beings. - Rabbi Moses ben Maimon, Physician and philosopher

In the killing of animals there is cruelty, rage, and the accustoming of oneself to the bad habit of shedding innocent blood. - Rabbi Joseph Albo, Sephardic philosopher