Proverbs 26:11 New English Translation

¹¹Like a dog that returns to its vomit,^[a]
so a fool repeats his folly.^[b]

Proverbs 26:11 sn The simile is graphic and debasing (cf. 2 Peter 2:22).
Proverbs 26:11 sn The point is clear: Fools repeat their disgusting mistakes, or to put it another way, whenever we repeat our disgusting mistakes we are fools. The proverb is affirming that no matter how many times a fool is warned, he never learns.

New English Translation (NET)