The rate of interest upon general pecuniary devises or pecuniary distribution under a trust instrument, unless otherwise provided in the will or trust instrument, shall be such as the supreme judicial court may by general rules establish, and in absence of any such rules the rate shall be 4 per cent per annum. Unless otherwise provided in the will or trust instrument, interest shall be payable from the date of the expiration of the period within which creditors may bring actions against a personal representative as provided in section 3-803.
Mass. Gen. Laws ch. 190B, § 3-904