N.J. Stat. Ann. § 40A:2-39

The proceeds of the sale of obligations shall be applied only to the purposes for which such obligations are authorized. If, for any reason, any part of such proceeds are not necessary for such purposes, such part shall be used to pay such outstanding obligations, or if in the opinion of the governing body it is in the best interest of the local unit such part may be appropriated to and used to finance the cost of any other purpose or purposes for which bonds may be issued.