ירמיהו, פרק י״ג, פסוק כ״ג

Vivid imagery from the natural world illustrates the profound grip of repeated sin. When negative behaviors are repeated over time, they shift from isolated actions into permanent habits. Eventually, correcting one's ways seems as difficult as altering the very laws of nature.

A powerful comparison is drawn from the physical world. Just as a dark-skinned person cannot change the color of his skin, and a leopard cannot shed its spots, a chronic sinner finds it nearly impossible to suddenly choose good. These physical traits are not accidental or temporary; they are natural and permanent features [רד״ק, מצודת דוד]. The spots of a leopard, which resemble the dark marks left by a deep bruise, are an inherent part of the animal [מצודת ציון, מלבי״ם]. There is even a subtle progression in these examples. While someone might argue that human skin color is merely a reaction to the hot sun and might theoretically change in a colder climate, the spots of a leopard represent an absolute, unchangeable reality that exists across the entire species under any condition [מלבי״ם].

This natural permanence mirrors the spiritual state of the Israelites. They have become so completely accustomed to doing wrong that evil has transformed into their second nature, making it seem as though they were born with it [רד״ק, מצודת דוד]. Because this wrongdoing has become ingrained in their very being, the punishment they face from God is not a random event. Instead, it is a direct, measure-for-measure consequence for forgetting Him and placing their trust in lies [מלבי״ם].

Despite this bleak comparison, the door to change is never fully closed. The absolute permanence of nature is used here as a deliberate exaggeration. It serves to highlight the immense struggle and extraordinary effort required to break deeply ingrained bad habits, rather than to suggest that returning to a good path is entirely impossible [מצודת דוד].