Since I am on the topic of Proverbs (see my previous post), I can’t resist sharing my favourite biblical proverb:

כְּ֭כֶלֶב שָׁ֣ב עַל־קֵאֹ֑ו
כְּ֝סִ֗יל שֹׁונֶ֥ה בְאִוַּלְתֹּֽו

Like a dog that returns to its vomit
is a fool who reverts to his folly (Proverbs 26:11)

An apt characterization of fallen human nature, in my humble opinion.