Let (l⊣i):L↪iE(l\dashv i):L\stackrel{i}{\hookrightarrow}E be a reflective subcategory of a topos such that the monad i∘li\circ l is cartesian (i.e. i∘li\circ l preserves pullbacks).
Then LL is a topos and ll preserves finite limits (i.e. (l⊣i)(l\dashv i) is a geometric morphism).