A transfer of real or personal property by a party in interest to a plan shall be treated as a sale or exchange if the property is subject to a mortgage or similar lien which the plan assumes or if it is subject to a mortgage or similar lien which a party-in-interest placed on the property within the 10-year period ending on the date of the transfer.
29 U.S. Code § 1106 - Prohibited transactions
(a) Transactions between plan and party in interestExcept as provided in section 1108 of this title:
(1) A fiduciary with respect to a plan shall not cause the plan to engage in a transaction, if he knows or should know that such transaction constitutes a direct or indirect—
(b) Transactions between plan and fiduciaryA fiduciary with respect to a plan shall not—
deal with the assets of the plan in his own interest or for his own account,
(c) Transfer of real or personal property to plan by party in interest