In any mortgage deed of real property, the words “upon statutory condition” or similar language, include the following conditions: “Provided, and this conveyance is made upon the express condition, if the mortgagor or his heirs, executors, administrators or assigns shall pay to the mortgagee or his heirs, executors, administrators or assigns the principal and interest of that certain promissory note or notes secured by this deed, at the time provided in said promissory note or in this deed, and shall also pay all taxes and assessments of every kind levied or assessed upon or in respect of the mortgaged premises or upon the note or notes secured thereby, then this deed, and also said promissory note, shall be absolutely void; otherwise the same shall remain in full force and effect.”