Mass. Gen. Laws ch. 184, § 21: Encumbrances upon real property; duty of grantor to inform grantee

Section 21. If real property upon which any encumbrance exists is conveyed by deed or mortgage, the grantor, in whatever capacity he may act, shall before the consideration is paid, by exception in the deed or otherwise make known to the grantee the existence and nature of such prior encumbrance so far as he has knowledge thereof.