In an early manuscript (probably late 1640s, when he would have been about 20), Robert Boyle put forward a number of arguments in favor of the humane treatment of animals. One of them was the Sabbath argument. Boyle notes that the Sabbath was instituted in part for the benefit of domestic animals:
Six days you shall do your work, but on the seventh day you shall rest; that your ox and your donkey may have rest, and the son of your servant woman, and the alien, may be refreshed.
He also notes that when God tells Jonah why he spares Nineveh, he mentions the cattle;
And should not I pity Nineveh, that great city, in which there are more than 120,000 persons who do not know their right hand from their left, and also much cattle?
Other arguments Boyle gives are that animals feel pain; that we can't rule out the possibility that animals have immortal souls; that because animals only have sensory pleasures and not our power for abstract pleasures, we should take into account in our treatment of them that their sensory pains are not sweetened by abstract pleasures about what the future will bring; that creation glorifies God; that those who mistreat animals get a bad reputation and develop bad habits; that animals are God's property and not ours; that they have value in themselves independent of their use to us (as shown in the fact that God had Noah save even the noxious animals; that, since there may be an excessive fondness for beasts, we have no reason to deny that there may be a deficient fondness for them as well; and that our Christian charity should be as broad as all creation.
Somewhat ironically, in later life Boyle was a vivisectionist, and tends to avoid the issue of humane treatment of animals.