Section 14A. An associate justice of the superior court, who has reserved his decision in a case heard by him without a jury, shall render his decision within four months from the date when the hearing was closed, or within such further time as the chief justice of said court may grant, upon a request in writing by such justice within said period, containing a full report of his reasons for not having rendered his decision and for requesting an extension of time for rendering his decision. A justice or special justice of a district court, other than the municipal court of the city of Boston, who has reserved his decision in a case heard by him, shall render his decision within a like period, or within such further time as the presiding justice of the appellate division of the court in which the case was heard may grant, upon a like request in writing, made by such justice or special justice within said period. An associate or special justice of the municipal court of the city of Boston, who has reserved his decision in a case heard by him, shall render such decision within a like period, or within such further time as the chief justice of said court may grant, upon a like request in writing, made by such associate or special justice within said period.