What is the legal standing of a pledge on the sold item if it is provided after the sale has become binding?

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If the pledge is offered after the sale becomes binding, the pledge is deemed valid. This is because it is valid for the buyer to pledge the item with someone other than the seller, so it is valid to pledge it with the seller. Furthermore, it is valid to pledge an item for a debt other than its price, so it is valid to pledge it for its own price.