Civ. Code, § 2924.5

No clause in any deed of trust or mortgage on property containing four or fewer residential units or on which four or fewer residential units are to be constructed or in any obligation secured by any deed of trust or mortgage on property containing four or fewer residential units or on which four or fewer residential units are to be constructed that provides for the acceleration of the due date of the obligation upon the sale, conveyance, alienation, lease, succession, assignment or other transfer of the property subject to the deed of trust or mortgage shall be valid unless the clause is set forth, in its entirety in both the body of the deed of trust or mortgage and the promissory note or other document evidencing the secured obligation. This section shall apply to all such deeds of trust, mortgages, and obligations secured thereby executed on or after July 1, 1972.