Noc from lendor for home loan

Hi, We have applied for a home loan from a co-operative bank. Our builder has been lent money for the project by IDBI bank whereas we are paying our installments to Union Bank. Hence, we need an NOC from IDBI bank for mortgaging the flat. The builder provided us with a letter they have from IDBI when asked for it. Below are the contents of the letter. Kindly help me in understanding what exactly this letter means. " Sub: No Objection Certificate for sale of flats / units in Plot C in respect of Facilities aggregating Rs. 1400 crores by Union Bank of India consortium. Please refer to your email dated July 13, 2015 on the captioned matter. In this connection, we have to inform that, as per the terms of clause 10.4 Indenture of Mortgage dated April 15, 2015, any sale of any flat / unit from the charge and mortgage created in favour of the Security Trustee shall be with prior written No Objection Certificate of the Lender's Agent i.e. Union Bank of India to be issued on behalf of all the Lenders. This is for your information and record purpose. " Thanks, Shwetha