Ijab need not originate with the seller. The first operative declaration may come from either party; the other party responds.
Example 1: Seller: “I have sold this book for 500 rupees.” Buyer: “I have bought it.”
Example 2: Buyer: “I have bought this book for 500 rupees.” Seller: “I have sold it.”
The goods, price and matching intentions must be clear in both cases.