Mass. Gen. Laws ch. 217, § 5: Oath of judge

Section 5. Each judge of probate, before entering upon the performance of his official duties, in addition to the oaths prescribed by the constitution, shall take and subscribe an oath that he will faithfully discharge said duties and that he will not during his continuance in office violate any provision of section six. Such oath shall be filed in the registry of probate of the county for which he is appointed.