Validity of a sale when the object is described incorrectly but physically pointed to?

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The sale is valid when the seller states, 'I have sold this wine to you' while pointing to vinegar, or states, 'This is Zayd's slave' while pointing to his own slave. The intended object referred to by the gesture is what is subject to the contract. This is because the object of the contract is valid for contracting upon, and its ruling is not altered by a difference in description, similar to cases where one says, 'I sold you this black one' while pointing to a white one, or 'This tall one' while pointing to a short one.