If so, why is it written "who is not betrothed"? It is "extra" for purposes of comparison and towards the formulation of a gezeirah shavah (identity), viz.: It is written here "who is not betrothed" and there (Devarim 22:28) "who is not betrothed": Just as there, fifty, so, here, fifty. Just as here, shekalim, so, there shekalim.