Riba (riba) ni kitendo cha kuchukua mali kwa mali nyingine ya aina hiyo hiyo kwa njia isiyo sawa. Sarf (ubadilishaji wa fedha) ni kitendo cha kuchukua mali kwa mali nyingine kutoka dhahabu na fedha za aina hiyo hiyo kwa usawa, au kutoka aina mbili tofauti kwa usawa au kwa upendeleo. Ubadilishaji huu unaweza kufanyika tu katika biashara; kuhusu riba, inaweza kutokea tu katika muamala wa biashara (Bay'u), katika mkopo (Qardh) au katika Salam (ununuzi wa mbele). Biashara (Al-Bay'u) ni kitendo cha kubadilishana mali kwa mali, ambacho husababisha mabadilishano ya mali; hili linaruhusiwa kwa sababu Allah (SWT) anasema:

Riba (usury) is the practice of taking property for another property of the same type unequally. The money exchange (Sarf) is the practice of taking a property for another property from gold and silver of the same type equally, or of two different types equally or preferentially. The exchange can only take place in trade, as for usury, it can only happen in a trade (Bay’u) transaction, in a loan (Qardh) or in a Salam (forward buying). Trading (Al-Bay’u) is the practice of exchanging property for property resulting in an exchange of property; this is permitted for Allah (swt) says:

“Na Mwenyezi Mungu amehalalisha biashara” [Al-Baqarah: 275]. Na kwa kuwa Bukhari alipokea kutoka kwa Hakeem Ibn Hizaam kwamba Mtume wa Allah ﷺ alisema: “Pande mbili za biashara zina haki ya kujiondoa (kutoka kwenye mkataba) isipokuwa zikitengana.” Kuhusu Salam, maana yake ni kukabidhi bidhaa papo hapo kwa ajili ya bidhaa iliyobainishwa itakayokabidhiwa wakati maalum baadaye (Ajal). Salam pia hujulikana kama Salaf (mkopo wa bidhaa). Ni aina moja ya biashara na inakubaliwa kwa njia ile ile kama biashara, lakini kwa maneno ya Al-Salam. Hii inaruhusiwa kwa sababu Allah (SWT) anasema:

“And Allah has made trading lawful” [Al-Baqarah: 275] And because Bukhari reported on the authority of Hakeem Ibn Hizaam that the Messenger of Allah (pbuh) said: “The two trading parties possess the right of withdrawal (from the deal) unless they separate.” As for the Salam, this means handing over a commodity immediately for a defined commodity which is to be handed over at a specific time in the future (Ajal). Salam also known as Salaf (credit). It is one type of trading and it is contracted in the same way as the trading, but with the wording of Al-Salam. This is permitted for Allah (swt) says:

"Unapojiingiza katika deni kwa muda maalum, liandike." [Al-Baqara: 282] Ibn Abbas alisema: "Nashuhudia kwamba Salaf (mkopo) wa dhamana, kwa tarehe maalum ya baadaye, umehalalishwa na kuruhusiwa na Allah ‘Azza Wa Jall", kisha akasoma aya hiyo:

“When you contract a debt for a fixed period, write it down” [Al-Baqarah: 282] Ibn Abbas said: “I bear witness that the guaranteed Salaf (borrowing), to a fixed future date, has been made lawful and allowed by Allah “Azza Wa Jall”, then He recited the verse:

"Unapokopa deni kwa muda maalum, liandike" [Al-Baqarah: 282]

“When you contract a debt for a fixed period, write it down” [Al-Baqarah: 282]

Pia kwa sababu Sheikh wawili (yaani Bukhari na Muslim) wameripoti kwa mamlaka ya Ibn Abbas aliyesema: "Mtume wa Allah ﷺ alipofika Madina watu walikuwa wakikopeshana na kukopa tende kwa miaka miwili au mitatu, hivyo akasema: 'Ikiwa mmoja wenu anakopesha kitu, na iwe kwa kipimo kinachojulikana au uzito unaojulikana na kwa muda unaojulikana.'" Kuhusu Qardh (mkopo), ni aina ya Salaf, nalo ni kumpa mtu mali ili amrudishie baadaye, na hili ni halali. Muslim ameripoti kwa mamlaka ya Abu Rafi'i kwamba "Mtume wa Allah ﷺ alikopa ngamia mchanga kutoka kwa mtu mmoja, kisha akapokea Sadaka kwa namna ya ngamia. Hivyo akamwamuru Abu Rafi'i ampe mtu yule ngamia wake mchanga; Abu Rafi'i akarudi kwake na kusema: 'Sikupata isipokuwa ngamia wa miaka minne.' Hapo akasema ﷺ: 'Mpe, kwani watu bora ni wale wanaolipa deni lao kwa namna iliyo bora.'" Ibn Hibban ameripoti kwa mamlaka ya Ibn Mas'ud kwamba Mtume wa Allah ﷺ alisema: "Hakuna Mwislamu atakayempa Mwislamu mwingine mkopo mara mbili, isipokuwa mmoja wao ataandikiwa kwake kama sadaka." Pia kwa sababu imethibitishwa kwamba Mtume wa Allah ﷺ alikuwa akikopa.

Also because the two Sheikhs (i.e. Bukhari & Muslim) reported on the authority of Ibn Abbas who said: “The Messenger of Allah (pbuh) arrived in Madinah while people were lending and borrowing dates over two or three years, so He (pbuh) said: ‘If any of you lends anything, let it be in a known measure or a known weight and for a known period of time.”’ As for the Qardh (loan), it is a type of Salaf, which is to give property to someone in order to restore it from Him later and this is lawful. Muslim reported on the authority of Abu Rafi’i “that the Messenger of Allah (pbuh) borrowed a young camel from a man, then He received Sadaqah in the form of camels. So He (pbuh) ordered Abu Rafi’i to give the man his young camel; Abu Rafi’i came back to Him and said: ‘I only found a four year old camel.’ Upon this He (pbuh) said: ‘Give it to him, for the best people are those who pay back their debt in the best manner.”’ Ibn Hibban reported on the authority of Ibn Mas’oud that the Messenger of Allah (pbuh) said: “No Muslim would give another Muslim a loan twice, except that one would be written for Him as charity.” Also because it has been established that the Messenger of Allah (pbuh) used to borrow.