The rhinoceros is known to be a short-tempered animal and, being an animal, follows its instincts and innate character by nature. The Hebrew word af, אף, can be used to describe two extremes in temperament: in the negative, it can refer to anger; and in the positive, when connoting tolerance and patience, as when G‑d is described as slow to anger, ארך אפים.

Controlling one’s anger is a trait that man learns from his Creator, since man was endowed by G‑d with the ability and self-control to harness his temperament. Man should also learn from this irate creature, the rhinoceros, how not to be. If man finds ridding himself of anger challenging, he should take small steps, a little at a time, while being confident that he will overcome and take control over this emotion.

From Nifla’os HaTeva, vol. 1, p. 63