Kubadilishana sarafu moja kwa sarafu ile ile au tofauti ni muamala wa kubadilishana, na ni halali. Hii ni kwa sababu kubadilishana ni kubadilisha fedha kwa fedha, dhahabu kwa fedha, ama sawa sawa katika aina moja, au tofauti kwa usawa katika aina tofauti. Kubadilishana huku hufanyika katika fedha kama inavyofanyika katika dhahabu na fedha, kwa sababu sifa za dhahabu na fedha zinatumika kwa fedha hizo kwa kuwa ni sarafu. Fedha si mfano wa dhahabu na fedha bali ni mojawapo ya aina zake, kwa kuwa inategemea mojawapo ya hizo mbili katika thamani yake ya kifedha. Kwa hiyo, mtu akinunua dhahabu kwa fedha, sarafu kwa sarafu, akisema kwa mfano: "Nimekuuzia Dinari hii ya dhahabu kwa Dirhamu hizi za fedha", akizitaja wakati wa kuuza wakiwa mbele yake, au akinunua dhahabu kwa fedha bila kuwepo, kama anapotia saini mkataba juu ya kitu cha fedha kilichoelezwa bila kuwepo, na akasema: "Nimekuuzia Pauni hizi za Misri kwa Dirhamu kumi za Hijazi", mifano hii ni halali, kwa kuwa fedha hizo zinabainishwa katika mikataba kwa kuzitaja, na hivyo umiliki wa mali zake unathibitika. Kwa hiyo, kubadilishana dhahabu kwa fedha ni halali, iwe ni Pauni kwa Dirhamu, vito vya fedha au kwa Niqar (yaani vumbi la fedha). Niqar ni sawa na Tibr (yaani vumbi la dhahabu) kwa upande wa fedha. Pia ni halali kubadilisha fedha kwa dhahabu, iwe ni vito, mabaki ya dhahabu au vumbi la dhahabu. Hata hivyo, biashara yote ya namna hii lazima ifanyike mkono kwa mkono na kwa kubainishwa, iwe ni sawa sawa au si sawa, uzito kwa uzito, au kiasi kinachojulikana (Jizaf) kwa kiasi kinachojulikana, au uzito kwa kiasi kinachojulikana katika aina zote zilizotajwa, mradi ubadilishanaji ni kati ya aina mbili tofauti, kwa kuwa kama zingekuwa za aina moja, zinaweza kuwa sawa tu na haziruhusiwi kuwa si sawa. Dhahabu inaweza kubadilishwa kwa dhahabu, iwe ni Dinari, vito, mabaki, madini ghafi, uzito kwa uzito, mali iliyoelezwa kwa mali iliyoelezwa, mkono kwa mkono, na kwa msingi hakuna tofauti inayoruhusiwa. Fedha pia inaweza kubadilishwa kwa fedha, iwe ni Dirhamu, vito vya mapambo au Niqar, uzito kwa uzito, mali iliyoainishwa kwa mali iliyoainishwa, mkono kwa mkono, na kimsingi hairuhusiwi tofauti yoyote. Hivyo, kubadilishana kati ya aina moja ya sarafu kunaruhusiwa, mradi iwe sawa, mkono kwa mkono na mali iliyoainishwa kwa mali iliyoainishwa. Kubadilishana kati ya sarafu mbili tofauti pia kunaruhusiwa, na katika hali hii sharti la usawa na tofauti halitumiki, lakini hii lazima ibadilishwe mkono kwa mkono, na mali iliyoainishwa kwa mali iliyoainishwa. Ushahidi wa kuruhusiwa kwa kubadilishana unatokana na Hadithi iliyopokewa na At-Tirmidhi kwa mamlaka ya Ubada bin As-Samit aliyesema kwamba Mtume wa Allah ﷺ alisema: "Mnaweza kubadilisha dhahabu kwa fedha mpendavyo, mkono kwa mkono." Muslim pia alipokea kwa mamlaka ya Ubada bin As-Samit aliyesema: "Nilimsikia Mtume wa Allah ﷺ akikataza kubadilisha dhahabu kwa dhahabu, fedha kwa fedha, ngano kwa ngano, shayiri kwa shayiri, tende kwa tende, chumvi kwa chumvi, isipokuwa kama ni kwa kiasi sawa na mali iliyoainishwa kwa mali iliyoainishwa. Yeyote anayeongeza au kuchukua ziada atakuwa ameingia katika riba." Muslim pia alipokea kwa mamlaka ya Abu Bakra aliyesema: "Alituamuru kununua dhahabu kwa fedha kadri tutakavyo, na kununua fedha kwa dhahabu kadri tutakavyo. Mtu mmoja alimuuliza ﷺ, naye akasema: 'Mkono kwa mkono'. Akaongeza: 'Ndivyo nilivyosikia'." At-Tirmidhi alipokea kwa mamlaka ya Malik bin Aws Al-Hadathan aliyesema: "Nilikuja nikiuliza ni nani angebadilisha baadhi ya Dirhamu, ndipo Talha bin Ubaydullah, alipokuwa ameketi pamoja na Umar bin Al-Khattab, akasema: 'Tuonyeshe dhahabu yako,' kisha urudi kwetu baadaye, mtumishi wetu atakapokuja tutakupa fedha yako (Dirhamu)." Hapo Umar alisema: “Hapana, kwa Allah, hutampa sarafu zake za fedha wala kumrudishia dhahabu yake, kwa sababu Mjumbe wa Allah ﷺ alisema: ‘Kubadilishana fedha kwa dhahabu kuna sehemu ya Riba isipokuwa kubadilishana mkono kwa mkono; ngano kwa ngano ni Riba isipokuwa mkono kwa mkono; shayiri kwa shayiri pia ni Riba isipokuwa mkono kwa mkono; na tende kwa tende pia ni Riba isipokuwa mkono kwa mkono.’”
Kwa hiyo, ni marufuku kufanya biashara ya dhahabu kwa fedha isipokuwa mkono kwa mkono, kwani ikiwa pande mbili za biashara zitaachana kabla ya kubadilishana mkono kwa mkono, ubadilishaji huo utakuwa haramu.
Al-Bukhari na Abu Dawud wamesimulia kwa mamlaka ya Umar kwamba Mjumbe wa Allah ﷺ alisema: “Kubadilishana dhahabu kwa fedha ni riba isipokuwa mkono kwa mkono.”
Ni sharti kwamba pande mbili za mkataba zikabidhiane papo hapo mahali pa mkataba, kwani zikiachana kabla ya kukabidhiana, mauzo hayo hayatazingatiwa kuwa yamefanyika kihalali. Hii ni kwa sababu ubadilishaji ni kubadilishana kwa bei, na kukabidhiana mahali pa mkataba ni sharti kuu la ubadilishaji kuwa sahihi.
Al-Bukhari amesimulia kwa mamlaka ya Malik Ibn Aws aliyesema: Mjumbe wa Allah ﷺ alisema: “Kufanya biashara ya dhahabu kwa fedha ni Riba isipokuwa mkono kwa mkono.” At-Tirmidhi pia amesimulia kwamba Mjumbe wa Allah ﷺ alisema: “Fanyeni biashara ya dhahabu kwa fedha mpendavyo, mradi tu ni mkono kwa mkono.”
Mjumbe wa Allah ﷺ alikataza biashara ya dhahabu kwa fedha kwa mkopo, na pia alikataza kubadilishana mali isiyokuwepo kwa mali iliyopo. Kwa hiyo, ubadilishaji lazima ufanyike mahali pa mkataba, kwani pande za mkataba zikiachana kabla ya kukabidhiana, ubadilishaji huo utakuwa batili kwa kukosekana kwa mojawapo ya masharti yake makuu. Lakini ikiwa sehemu ya biashara ilibadilishwa mahali pa biashara, basi biashara itakuwa sahihi katika sehemu iliyobadilishwa na sawa yake katika malipo, na itakuwa batili kwa sehemu iliyobaki ya biashara na sehemu yake sawa. Hii ni kwa sababu inaruhusiwa kugawanya biashara katika sehemu. Kwa mfano, mtu akibadilisha Dinari moja kwa Dirhamu kumi na mtu mwenye Dirhamu tano tu, itakuwa batili kwao kutengana kabla Dirhamu kumi zote hazijalipwa. Ikiwa Dirhamu tano zililipwa kisha wakatengana, ubadilishaji utakuwa batili kwa nusu ya Dinari na sahihi kwa nusu nyingine ambayo ni sawa na Dirhamu tano zilizolipwa. Hii ni kwa sababu inaruhusiwa kugawanya biashara ya mauzo. Ikiwa mwenye Dirhamu tano alikopa kiasi kilichobaki cha fedha kutoka kwa mtu mwingine au kutoka kwa mtu wa tatu ili kukamilisha biashara, ubadilishaji utakuwa sahihi, mradi kukopa hakukuwa sharti katika biashara; kwa maana kama kilikuwa sharti katika biashara, biashara ingekuwa batili.
The sale of one currency for the same or a different currency is a transaction of exchange, and it is permitted. This is because exchange is the swapping of money for money, of gold and silver, either equally in the same type, or differently and equally in the different types. The exchange takes place in the money as it takes place in gold and silver, for the description of gold and silver applies to it in its quality as a currency. Money is not analogous to gold and silver but is one of its forms, for it is based on either of them in their monetary valuation. So if a person were to purchase gold for silver, coin for coin, by saying for instance: “I sold to you this golden Dinar for these silver Dirhams”, by naming them while present at the time of sale, or if He were to purchase gold for silver while not present such as when signing a contract over a described monetary item while not being present, and He says: “I sold to you these Egyptian pounds for ten Hijazi Dirhams”. These examples are permitted, for the monies are determined in the contracts by naming them, thus the ownership of their assets is established. Therefore, trading gold for silver is permitted, whether this was pounds for Dirhams, silver jewellery or for Niqar (i.e. silver dust). The Niqar is the silver equivalent of Tibr (i.e. gold dust). It is also permitted to trade silver for gold, whether jewellery, bullion or gold dust. However, all such trade must be conducted hand to hand and described, either equally or unequally, weight for weight, or known quantity (Jizaf) for known quantity, or weight for known quantity in all the mentioned types, provided the exchange is in two different types, for if they were from the same type, they can only be equal and must not be unequal. Gold could be traded for gold, whether this were Dinars, jewellery, bullion, ore, weight for weight, described asset for described asset, hand to hand, and in principle no difference is permitted. Silver could also be traded for silver, be it Dirhams, jewellery or Niqar, weight for weight, described asset for a described asset, hand to hand, and no difference is allowed in principle. Therefore, the exchange between the same type of currency is permitted, provided that it is equal, hand to hand and a described asset for a described asset. The exchange between two different currencies is also permitted and in this case, the condition of equality and disparity does not apply, but this must be exchanged hand to hand, and a described asset for a described asset. Evidence for the permissibility of exchange is derived from the Hadith reported by At-Tirmidhi on the authority of Ubada ibn As-Samit who said that the Messenger of Allah (pbuh) said: “You may trade gold for silver as you wish, hand to hand.” Muslim also reported on the authority of Ubada ibn as-Samit who said: “I heard the Messenger of Allah (pbuh) forbid the trading of gold for gold, silver for silver, wheat for wheat, barley for barley, dates for dates, salt for salt, unless this was in equal quantities and described asset for a described asset. He who increases or takes an increase would fall into usury (Riba).” Muslim also reported on the authority of Abu Bakra who said: “He has ordered us to buy gold for silver as we wished, and to buy silver for gold as we wished. A man asked Him (pbuh) so He said: “Hand to hand”. He added: “That is how I heard it.” At-Tirmidhi reported on the authority of Malik Ibn Aws Al-Hadathan who said: “I came asking who would exchange some Dirhams, whereupon Talha Ibn Ubaydullah as He was sitting with Umar ibn al-Khattab, said: ‘Show us your gold,’ and then come to us at a later time, when our servant would come we would give you your silver (Dirhams).” Upon this Umar said: “No by Allah, you shall give Him his silver coins or return his gold to him, for the Messenger of Allah (pbuh) said: ‘Exchange of silver for gold has an element of Riba in it unless it is exchanged hand to hand, wheat for wheat is Riba unless it is hand to hand, barley for barley is also Riba unless it is exchanged hand to hand and dates for dates is also Riba unless it is hand to hand.”’ It is therefore forbidden to trade gold for silver except hand to hand, for if the two trading parties parted company before they exchanged hand to hand, the exchange would be unlawful. Bukhari and Abu Dawud reported on the authority of Umar that the Messenger of Allah (pbuh) said: “Exchanging gold for silver is riba except hand to hand.” It is conditional that the two contracting parties cash in at the place of the deal, for once they separated prior to the cashing in, the sale would not lawfully be considered to have taken place. This is because the exchange is the inter-trading of prices, and to cash in at the place of the deal is a prime condition for the exchange to be valid. Bukhari reported on the authority of Malik Ibn Aws who said: The Messenger of Allah (pbuh) said: “Trading gold for silver is Riba unless it is hand to hand.” At- Tirmidhi also reported that the Messenger of Allah (pbuh) said: “Trade gold for silver as you wish, as long as it is hand to hand.” The Messenger of Allah (pbuh) prohibited the trading of gold for silver in credit, and also prohibited the trading of an absent asset for a present one. Therefore, the exchange must take place at the place of the deal, for if the contracting parties separated before cashing in, the exchange would be invalid due to the non-fulfilment of one of its main conditions. If however, part of the deal was exchanged at the place of the deal, the deal would then be valid in the part which was exchanged and, its equivalent on the recompense and it would be invalid for the remainder of the deal and its equivalent part of the deal. This is because it is permitted to divide the deal into parts. For instance, if a person exchanged one Dinar for ten Dirhams with a person who has only five Dirhams, it would be invalid for them to separate before the full ten Dirhams are cashed in. If the five Dirhams were cashed in and they separated, the exchange would be invalid for half the Dinars and valid for the other half which is equivalent to the five Dirhams that have been cashed in. This is because it is permitted to divide the deal of sale. If the person with the five Dirhams borrowed the remainder of the money from the other person or a third party, to complete the deal, the exchange would be valid, as long as the borrowing was not a condition in the deal, for if it was a condition in the deal, the deal would be invalid.