Section: If a man enters into a currency exchange with another for one dinar against ten dirhams, and he has with him only five dirhams, it is not permissible for them to separate before taking possession of all ten. If he takes possession of the five and they separate, the currency exchange for half of the dinar is void. As to whether it is void regarding what corresponds to the five that were taken into possession, there are two opinions, based on the principle of splitting the transaction (tafriq al-safqa). If he wishes to avoid this, they may rescind the exchange for the half for which he does not have the compensation, or they may rescind the entire contract; then he buys from him half the dinar for five, hands it over to him, and takes the entire dinar. Thus, what he purchased from him belongs to him, and the remainder is held in trust (amanah) in his hand, then they separate. Thereafter, if he exchanges the remainder of the dinar with him after that, or buys something from him with it, or makes it a deferred delivery contract (salam) for something, or gives it to him as a gift, it is permissible, and likewise if he appoints him as an agent for it. If he buys silver with a dinar and a half, and gives the seller two dinars, saying: "You are my agent for the extra half dinar," it is valid. If he exchanges ten dirhams with him for a dinar, and gives him more than a dinar in order for him to weigh out his due at another time, it is permissible, even if it takes a long time, and the excess is a trust in his hand, and he bears no liability if it is destroyed. Ahmad stipulated most of these issues. If one of them has only five dirhams, and he buys half a dinar with them, and takes possession of a full dinar, and hands the dirhams over to him, then borrows them from him, and buys the remaining half with them, or buys the dinar from him for ten from the outset and hands the five to him, then borrows them from him and hands them to him as compensation for the other half, without it being a pretext (hilah), then there is no harm in it.

Section: If one sells two mudds of poor-quality dates for a dirham, then buys choice dates with the dirham, or buys a sound dinar from a man for dirhams, and they take possession of them, then buys scraps (qurada) from him with the dirhams without prior collusion or pretext, there is no harm in it. Ibn Abi Musa said: It is not permissible, unless he goes to someone else to buy from him and it does not work out for him, in which case it is permissible...