53. Trustee may not buy beneficiary' s interest without permission.- No trustee, and no person who has recently ceased to be a trustee, may, without the permission of a principal Civil Court of original jurisdiction, buy or become mortgagee or lessee of the trust- property or any part thereof; and such permission shall not be given unless the proposed purchase, mortgage or lease is manifestly for the advantage of the beneficiary. Trustee for purchase. Trustee for purchase.- And no trustee whose duty it is to buy or to obtain a mortgage or lease of particular property for the beneficiary may buy it, or any part thereof, or obtain a mortgage or lease of it, or any part thereof, for himself.