Maimonides, Guide for the Perplexed III, 17
The underlying objective to refrain from tza’ar ba’alei chayim is established with a view to perfecting us that we should not acquire moral habits of cruelty and should not inflict pain gratuitously, but that we should intend to be kind and merciful even with an individual animal except in the case of need.

Suggested Discussion Questions:

What does Maimonides mean by 'except in the case of need'?

Does this imply that we can afflict baboons in medical experiments? Or test our cosmetics in the eyes of rabbits?

Time Period: Medieval (Geonim through the 16th Century)