Massachusetts General Laws Part I. Administration of the Government (Ch. 1-182) Ch. 175, § 183

No person shall receive or accept from any company or officer or agent thereof, or any insurance broker, or any other person, any such rebate of premium paid or payable on the policy or contract, or any special favor or advantage in the dividends or other benefits to accrue thereon, or any valuable consideration or inducement not specified in the policy or contract or any policy of workers' compensation insurance, or any motor vehicle liability bond or any motor vehicle liability policy, both as defined in section thirty-four A of chapter ninety, at a rate different from that fixed, established or approved by the commissioner.  No person shall be excused from testifying, or from producing any books, papers, contracts, agreements or documents at the trial of any other person charged with violating any provision of this and the preceding section, on the ground that such testimony or evidence may tend to incriminate himself;  but no person shall be prosecuted for any act concerning which he shall be compelled so to testify or produce evidence, documentary or otherwise, except for perjury committed in so testifying.