。
If you're not brave, you won't win the beauty.
Literal
Brave-person [copula-に] not-being-[archaic-conditional-ずんば] beauty [object-を] not-obtain-[archaic-negative-ず].
Entirely classical: あらずんば contracts あらざれば ('if not being'), using the classical negative ず in a conditional. 得ず ('not obtain') uses the same classical negative. This is a Japanese rendering of the Western proverb 'fortune favors the bold,' recast with 美女 as the prize. The archaic grammar marks it unmistakably as a proverb.