This may be used as a legal stratagem for selling gold in exchange for silver on deferred terms, which is impermissible.
His statement, “or after receiving its price,” means that if he buys it back for less after receiving its price, there is no harm in it. The same applies if he buys it back for more or for the same price.
For example, he sells a car for twenty thousand payable in one year. When the year has elapsed, he receives the twenty thousand, then buys the car back from the purchaser for fifteen thousand. This is permissible, because the possibility of a legal stratagem is absent here. Thus, if he buys it back for less than he sold it for after receiving the price, there is no harm in it.
His statement, “or after a change in its condition,” may be illustrated as follows: I sell him a fat cow for one hundred dirhams payable in six months. After three months have passed, the cow becomes emaciated and is worth only half its value. The seller then buys it back for half its value—that is, for less than he sold it for in cash. The author says that there is no harm in this, because the reduction here is not in exchange for the deferred payment, but rather in exchange for the change in its condition.
However, this should be qualified: the difference between the two prices must correspond to the amount by which the item has depreciated due to that change, not to the difference between deferred payment and cash payment. The reduction in price must therefore be proportionate to the reduction in its condition.
For example, if we suppose that this cow became emaciated and, after having been worth two hundred on deferred terms, would now be worth one hundred and eighty if sold, and he bought it back at this price, then this is permissible, because the reduction is in exchange for the diminished condition. But if it had depreciated by only twenty due to its condition, while he bought it back for one hundred and sixty, with the additional difference of twenty being due to the difference between deferred payment and cash payment, then this is forbidden, because the difference that has now arisen between