无论交易所得的兑换形式多么繁多多样,它们始终只限于同类货币之间的兑换,或不同类货币之间的兑换。交易只能发生在现金与现金之间,或在延期支付(Dhimma,即信用)与另一延期支付之间。现金与信用之间不能进行兑换。兑换交易一经缔约并完成交割,即告生效,缔约双方都不能反悔,除非确定存在严重的欺诈或瑕疵,在这种情况下,允许缔约一方撤销交易。例如,如果缔约一方发现所购之物有瑕疵,比如他发现所买的白银中掺有铜,或白银变黑,他可以选择退回所买之物,或按交易时约定的价格接受。这意味着,只要退货的汇率与交易时的汇率相同,退货是被允许的。如果缔约一方接受了这些货物,交易即有效;如果他决定退回,交易则取消。例如,若有人用24K金换取24K金,却发现所购之金实为18K,这便构成欺诈,此时他可以选择按交易时约定的兑换价格接受交易,或拒绝交易。因此,如果以金换金的人决定打折接受这有瑕疵的黄金,这是不允许的,因为这样会使两种商品中的一方被赋予更高的价值,从而缺乏等值性,而等值性正是"同类"交易的一个条件。

No matter how numerous and varied the transactions of exchange are, they would always be confined to the trading of one currency for another of the same type, or the trading of one currency for another of a different type. The transaction only occurs either between ready cash for other ready cash, or between a Dhimma (credit) for another credit. The exchange cannot take place between cash and a credit. When the exchange transaction takes place, it becomes effective once the contracts and the cashing in have taken place, and neither of the two contracting parties can go back on his word, unless it became established that there had been a case of serious fraud or defect, in which case it is permitted for one of the contracting parties to withdraw from the deal. If, for instance one of the contracting parties found a defect in that which He had purchased, for example He found that the silver He had bought contained copper, or that the silver turned black, He has the option to return the goods He had bought or to accept them based on the agreed price at the time of the transaction. This means that the returning of goods is allowed as long as it is at the same rate as the time of the deal. If one of the contracting parties accepted the goods, the transaction would be valid, and if He decided to return them, the deal would be cancelled. If, for instance one bought 24 carat gold for 24 carat gold, only to find that the gold purchased is only 18 carats, this would be considered fraud, and in this case He would have the choice of either accepting the deal at the agreed price of exchange at the time of the transaction or rejecting it. So, if the person who exchanged the gold for gold decided to accept the gold with its defect at a discount, this would not be allowed because there would be a higher value placed on one of the two commodities, and there is an absence of equivalence which is a condition of a deal of the “same type”.

另一个例子是：一名负债者对其债务人说：“请减免我一部分债务，我会尽快偿还剩余的债务。”这同样是不被允许的，因为这等同于将现货交易与远期交易进行不等值的交换，即负债者实际上是把自己的债务“即时”卖给了债务人，且price低于原始交易，从而造成了价值差异，而这就是利息（Riba）。同样，如果债务人对负债者说：“如果你提前偿还你欠我的100，我会给你10迪拉姆。”这也是不被允许的，因为其中存在价值上的差异，即利息（Riba）。 穆斯林（Muslim）引述艾卜·赛义德·胡德里（Abu Sa'id Al-Khudri）的传述说：安拉的使者ﷺ说：“黄金换黄金、白银换白银、小麦换小麦、大麦换大麦、椰枣换椰枣、盐换盐，要等量交换，并且须当场交割。谁增加或取得增额，谁就陷入了利息（Riba），无论是取得者还是给予者。” 另一个例子是：甲欠乙黄金，乙欠甲白银，二人互相抵偿各自所欠，即甲用黄金偿还所欠，同时以白银收回自己应得的债务。这种交换是合法的，因为债务的即时偿付与商品的即时交付相似。此外，如果有人以黄金购买货物，而卖方以白银收取货款，这种交易也是被允许的，因为以一种货币偿还另一种货币是可以的，这笔交易属于以资产与债务（信用）进行的交换。这是因为艾布·达乌德（Abu Dawud）和阿塞拉姆（Al-Athram）在其《圣训集》（Sunan）中引述伊本·欧麦尔（Ibn Umar）的传述说：他说：“我过去在白尔奇（Baqee'）经营骆驼买卖，我会以第纳尔（Dinars）出售，而以迪拉姆（Dirhams）收款；或以迪拉姆出售，而以第纳尔收款。” 那么我把这个换成那个，于是我去见安拉的使者ﷺ，他在哈芙赛的家中，我说：“安拉的使者ﷺ啊，请您听我说，我想问您一件事。我在拜格尔（Baqee’）卖骆驼，我以第纳尔（Dinars）计价，以迪拉姆（Dirhams）收款，或者我以迪拉姆计价，以第纳尔收款。我拿这个换那个，给这个换那个。”安拉的使者ﷺ回答说：“这没有问题，只要你们按当天的市价交易，并且在双方之间没有任何未结清的款项时就分开。” 另外，如果一个人用两枚假第纳尔从另一人那里买一枚真第纳尔，这是不允许的。然而，如果他用银迪拉姆买一枚真第纳尔，然后用这些迪拉姆买两枚假第纳尔，无论是从同一个人还是从另一个人那里买，这都是允许的。这是因为穆斯林（Muslim）转述了艾布·赛义德（Abu Sa’id）的话，他说：“比拉勒（Bilal）带着一些优质的巴尔尼（Barni）枣子来见安拉的使者ﷺ，安拉的使者ﷺ问道：‘这是从哪里来的？’比拉勒回答说：‘这是我们之前留下的一些劣质枣子，我用两萨阿（sa’a）劣质枣子换了一萨阿优质枣子，作为安拉的使者ﷺ的食物。’”于是安拉的使者ﷺ说：“哎呀！这正是真正的高利贷（Riba），所以不要这样做。如果你想买（优质的）枣子，可以先把（劣质的）枣子在另一笔交易中卖掉，然后再买（优质的）枣子。” 此外，艾布·赛义德和艾布·胡莱赖（Abu Hurairah）在一段“公认的”圣训中转述：“安拉的使者ﷺ任命一个人为海巴尔（Khaybar）的税务官，有一天他带着一些叫做贾尼布（Janeeb）的优质枣子来见安拉的使者ﷺ。安拉的使者ﷺ说：‘海巴尔的枣子都是这样的吗？’他说：‘不是的，凭安拉发誓，安拉的使者啊！ 我们用一萨阿的这种优质枣子，换取两萨阿劣质枣子，再用两萨阿换取三萨阿。”于是先知穆罕默德ﷺ说：“不要这样做；你应当把你手中的劣质枣子卖掉换成迪拉姆，然后用迪拉姆购买贾尼卜枣。”在这里，先知穆罕默德ﷺ并没有命令此人把枣子卖给别人，而不卖给他向其购买的那个人。如果把枣子卖给同一个向你购买的人是哈拉姆的，那么先知穆罕默德ﷺ就会向他的税吏解释这一点。因此这是被允许的，因为他用一种物品（枣子）换取另一种物品（枣子），没有任何先决条件或秘密协议（默契），所以是允许的，就好像他是从另一个人那里购买的一样。同样，用黄金换白银，然后再买白银，也是允许的。然而，如果这是以事先安排和秘密交易为前提的，那就不被允许，并且会被视为被禁止的诡计。这是因为伊斯兰教禁止并不合法任何形式的欺诈，即以欺骗手段使合同看似合法，而意图实施被禁止的行为。这包括唆使做出安拉所禁止的行为、怠慢安拉（SWT）所命令的行为、侵占应有权利等。因为通往哈拉姆的途径本身就是哈拉姆。另外，艾哈迈德转述乌巴达·伊本·阿斯-萨米特的传述说，先知穆罕默德ﷺ说：“我的乌玛中将有一群人，他们在给酒（海믈尔）换一个名字之后，会认为它是合法的。”艾哈迈德还转述阿布·马立克·阿施አ'ari的传述说，他听到先知穆罕默德ﷺ说：“我的乌玛中的人将饮用酒（海믈尔），却给它起了另一个名字。”因此，交易是伊斯兰教中合法的交易之一，但须遵循沙里亚所规定的特定规则。它既可以在本地交易中进行，也可以在对外交易中进行。 正如金与银、银与金之间在同一国家货币内的兑换一样,这种兑换也可以用外币进行,无论是在国内还是在国外,无论这些兑换是货币性的还是商业性的,也无论涉及的是哪一种货币对另一种货币的兑换。为了详细阐述各种货币之间的外汇交易,我们需要深入研究货币的本质。

Another example would be if an indebted person said to his debtor: “Reduce some of my debt and I will hurry in repaying the remainder of the debt.” This is also not allowed because it would be the trading of a ready sale for a future sale without equivalence i.e. it is as if the indebted person sold his debt “promptly” to his debtor for less than the original transaction, thus creating a disparity which is Riba. Likewise, if the debtor said to the indebted: “I would give you ten Dirhams if you accelerated the repayment of the 100 you owe me”, this is not allowed because there would be a disparity in the value which is Riba. Muslim reported on the authority of Abu Sa’id Al-Khudri that the Messenger of Allah (pbuh) said: “Trade gold for gold, silver for silver, wheat for wheat, barley for barley, dates for dates and salt for salt, like for like, and hand to hand, for whoever increases or takes an increase will fall into riba, for the taker and the giver alike.” Another example would be if one person owed another gold and the latter owed the former silver, and they exchanged what each owed the other i.e. if the former settled what He owed in gold with what He is owed in silver, this type of exchange would be lawful, for the immediate payment of debt is like the immediate payment of goods. Also, if a person bought goods in gold, and the seller cashed the value of the goods in silver, this type of transaction would be permitted, for it would be permitted to pay off one of the currencies by another currency, and this deal would be an exchange with an asset and debt (credit). This is because Abu Dawud and Al-Athram reported in their “Sunan” on the authority of Ibn Umar who said: “I used to trade in camels in the Baqee’, so I would sell in Dinars and get paid in Dirhams, or sell in Dirhams and get paid in Dinars. I would take this from that and give this from that, so I went to the Messenger of Allah (pbuh) at Hafsa’s house, and I said: ‘O Messenger of Allah (pbuh) will you please listen, I want to ask you something. I sell camels in the Baqee’, I sell in Dinars and get paid in Dirhams or I sell them in Dirhams and get paid in Dinars. I take this from that and give this from that.’ The Messenger of Allah (pbuh) answered: ‘There is nothing wrong in this as long as you trade according to the market value of the day and as long as you do not part company from the other party with something still outstanding between the two of you.”’ Also, if a person bought from another a genuine Dinar for two fake Dinars, this would not be allowed. However, if He bought a genuine Dinar for silver Dirhams, then bought with the Dirhams two fake Dinars, this would be allowed whether He bought them from the same person or from another. This is so because Muslim reported on the authority of Abu Sa’id who said: “Bilal came to the Messenger of Allah (pbuh) with some Barni (fine quality) dates, so the Messenger of Allah (pbuh) enquired: ‘Where did this come from?’ Bilal replied: ‘These are dates of inferior quality we had for some time, and I exchanged two sa’as of inferior quality for one sa’a of fine quality as food for the Messenger of Allah (pbuh).”’ Upon this the Messenger of Allah (pbuh) said: “Woe! this is real Riba so do not do that. If you wish to buy dates (of superior quality) you could sell the dates (of inferior quality) in a separate bargain and then buy the (superior quality dates).” Also, Abu Sa’id and Abu Hurairah reported in an “agreed upon” Hadith “that the Messenger of Allah (pbuh) appointed a man as a tax collector over Khaybar, so He came to Him one day with some fine quality dates called Janeeb. Upon this the Messenger of Allah (pbuh) said: ‘Are all the dates of Khaybar like this?’ He said: ‘No, by Allah, O Messenger of Allah! We buy one Sa’a of these fine quality dates for two Sa’as of inferior dates and also two Sa’as of it for three Sa’as.”’ Upon this the Messenger of Allah (pbuh) said: “Do not do this; rather sell the inferior quality of dates you have for dirhams and then buy the Janeeb dates with the use of dirhams.” Here, the Messenger of Allah (pbuh) did not order the man to sell his dates to a person other than the one He would buy them from, and if the selling of dates to the same person He buys from was Haram then the Messenger of Allah (pbuh) would have explained this to his tax collector. It was therefore permitted because He sold one type of good (dates) for another type (dates) without any preconditions or secret agreement (connivance) so it is allowed, as if He had bought from another person. Likewise, it would be permitted to sell gold for silver, and then buy silver. However, if this were subject to a prior arrangement and secret deals, it would not be allowed, and it would be regarded as a prohibited ploy. This is because any type of trickery is prohibited and unlawful in Islam i.e. any attempt to portray a contract as legitimate with the intent to commit a forbidden act using deception. This includes soliciting an action that Allah has forbidden, neglecting an action that Allah (swt) has commanded, suppressing a right etc. This is because whatever leads to Haram is itself Haram, and because Ahmed reported on the authority of Ubada Ibn As-Samit that the Messenger of Allah (pbuh) said: “A group from my ummah will one day consider “khamr” (intoxicants) lawful after they give it a different name.” Ahmed also reported on the authority of Abu Malik Al-Ashja’i who said that He heard the Messenger of Allah (pbuh) say: “People from my ummah will drink alcohol (Khamr) while giving it a different name.” Therefore, exchange is one of the lawful transactions in Islam according to specific rules determined by the Shar’a. It can be conducted in local transactions as well as foreign. Just like the exchange of gold for silver and silver for gold of the same currency of the country, this can also be performed in a foreign currency, whether at home or abroad, and whether the exchanges were monetary or commercial as well as where the exchange of a currency for another is involved. In order to elaborate on the foreign exchange between various currencies, we need to study in depth the nature of money.