Massachusetts General Laws Part II. Real and Personal Property and Domestic Relations (Ch. 183-210) Ch. 183, § 38

A person interested in a deed which has not been acknowledged may, before or during proceedings before a court for proof of its execution, file in the proper registry of deeds a copy thereof, compared with the original by the register; and the filing of such copy shall for thirty days thereafter have the same effect as the recording of the deed, if the deed is within that time duly proved and recorded; or if, at the expiration of said thirty days, such proceedings are pending, the effect of filing such copy shall continue until the expiration of seven days after the termination of such proceedings.