Section 3(2)(iv) in The Delhi Development Authority Rules, 1958
(iv)the sale to the Authority or to any officer or other employee of the Authority on behalf of the Authority, of any article in which he regularly trades or the purchase from the Authority, or from any officer or other employee on behalf of the Authority, of any article of a value in either case not exceeding five thousand rupees in the aggregate in any year during the period of contract or work; or