Mass. Gen. Laws ch. 127, § 157

If a prisoner is pardoned or his punishment is commuted, the officer to whom the warrant for such purpose is issued shall, as soon as may be after executing it, make return thereof, signed by him, with his doings thereon, to the secretary's office, and shall file in the office of the clerk of the court in which the offender was convicted an attested copy of the warrant and return, and the clerk shall subjoin a brief abstract thereof to the record of the conviction and sentence.