According to mythical tales, panthers were thought to be so gentle only dragons were their enemies.
It is well known that not only biblical sources inform Christian iconography. Many old legends were compiled in the Physiologus, a didactic Christian text written or compiled in Greek by an unknown author, consisting of descriptions of animals, birds, and fantastic creatures, sometimes stones and plants, provided with moral content, and dated somewhere around the end of the 2nd or 3rd century.
In fact, the Physiologus became quite popular during the Middle Ages, as it included commentaries from Aristotle and Pliny the Elder on zoology. It served as a primary source for the work of later writers, such as St. Isidore of Seville and St. Ambrose, who would then associate certain moral virtues (and vices, of course) with various animals, based on references in Scripture, tradition and other literary sources.