N.J. Stat. § 2A:50-49
Whenever it is provided in a mortgage that the owner of the mortgaged premises shall keep the same insured for the benefit of the mortgagee and that, in default thereof, or upon the failure, neglect or refusal of the owner to pay any premium for such insurance protection, the mortgagee may either procure such insurance or pay any such defaulted premium in order to preserve the protection of his insurance, and add the cost of procuring such insurance or the amount paid by him for any such premium to the principal sum due on the mortgage, to be recovered upon demand or otherwise with interest from the date of such procurement or payment, or the mortgagee is given the option to declare the principal sum due on the mortgage whenever the owner fails to furnish proper insurance protection, the holder of the mortgage may, upon paying for or procuring such insurance, waive the demand for the payment of the principal sum due on the mortgage and foreclose the mortgage only for the amount paid by him to procure such insurance, with interest thereon from the date of such payment.
N.J.S. § 2A:50-49