Section 17(2)(b) in The Reserve Bank of India Act, 1934
(b)the purchase, sale and rediscount of bills of exchange and promissory notes, drawn and payable in India and bearing two or more good signatures, one of which shall be that of a scheduled bank or a State co-operative bank or any financial institution, which is predominantly engaged in the acceptance or discounting of bills of exchange and promissory notes and which is approved by the Bank in this behalf and drawn or issued for the purpose of financing agricultural operations or the marketing of crops, and maturing within fifteen months from the date of such purchase or rediscount, exclusive of days of grace;