A crow is never the whiter for washing herself often.

Repeated attention to outward appearance does not necessarily change a person's underlying character or conduct. Washing cannot make the crow's feathers white.

The proverb draws a distinction between looking improved and being improved. It cautions against treating visible efforts to appear respectable as proof that a deeper fault has been corrected.

Use the proverb to question repeated attempts to improve an appearance or reputation when the behavior at issue remains unchanged. It is a pointed criticism, so it suits a judgment about conduct better than an attempt to encourage someone.