"Ka ba ma'aikaci ladansa kafin gumin jikinsa ya bushe." (Ibn Maja ne ya ruwaito shi); wato, ya kamata ma'aikaci ya karbi albashinsa idan ya gama aikinsa, ko menene yanayin wannan ladan.
Bugu da kari, wadannan abubuwa da ake amfani da su wajen musaya ba ayyuka ba ne da asalinsu za a takaita su (bisa dalili), don haka izininsu zai bukaci dalili, sai dai abubuwa ne kawai. Asalin al'amarin abubuwa shi ne cewa halal ne matukar babu dalilin haramta su, kuma babu wani dalili da aka ruwaito da ke haramta amfani da wani abu a matsayin musaya. Saboda haka, halal ne a gudanar da mu'amalolin Shari'a da su, ko sayarwa ko saye ko bayarwa kyauta ko musaya, sai dai duk abin da akwai nassi da ya haramta musayarsa.
Bisa wannan, musayar kaya da kudi, da kudi da kaya, halal ne ba tare da wani takura ba, sai dai musayar kudi da kudi saboda tana da ka'idoji na musamman, don haka ana takaita ta da wadannan ka'idoji. Hakazalika, musayar aiki da kudi, da kudi da aiki, halal ne ba tare da takura ba, matukar kayan ko hidimar ba a ambace su a cikin nassi a matsayin haramtattu ba. Saboda haka, musayar kaya da wani nau'in kudi na musamman, haka ma musayar hidima ko aiki da wani takamaiman adadin kudi, halal ne ba tare da wani takura ba, komai irin naúrar wannan kudin. Don haka, ko naúrar kudin ba ta da wani abu da ke goyon bayanta, kamar kudin fiat, ko an tallafa mata da wani adadi na zinare, kamar takardar kudi da aka tabbatar da ita da zinare, ko kuma naúrar da aka tallafa ta da zinare da azurfa daidai darajarta, kamar takardar kudi mai wakiltar zinare, duk ana ganin halal ne a yi musaya da su. Saboda haka, daidai ne a musanya kaya ko hidima da kowace naúrar kudi, kuma halal ne Musulmi ya sayar da kowane kudi, ya saya da kowane kudi, ya yi hayar aiki da kowane kudi, ko kuma ya yi aiki a kan kowane kudi.
“Give the worker his wages before his sweat dries.” (reported by Ibn Maja); in other words, that the worker should receive his salary when he finishes his work, whatever the nature of that wage. Additionally, these things that are used for exchange are not actions such that they would in origin be restricted (to the evidence) and so their permission would require an evidence, but rather they are things. The origin regarding things is that they are permitted as long as there is no evidence to prohibit them, and there is no evidence reported which prohibits using anything as an exchange, and so accordingly it is permitted to carry out Shari’ah transactions with them whether buying and selling, giving as a gift or exchanging with the exception of anything where there is a text prohibiting its exchange. Based upon this, exchanging goods for money, and money for goods is permitted without any restrictions, except for exchanging money with money because it has specific rules and so it is restricted by those rules. In the same manner, exchanging effort for money, and money for effort, is permitted without restriction unless the goods or service have been mentioned in a text as being forbidden. Accordingly, to exchange goods for a specific form of money, and in the same manner to exchange a service or effort for a specific unit of money, is also permitted without any restriction, whatever the unit of that money may be. So irrespective of whether that unit doesn’t have anything backing it, such as fiat currency, or if it was backed by a specific amount of gold , such as secured paper currency, or if the unit was backed by gold and silver to its value such as representative paper currency, all of them are considered to be allowed to trade with. Therefore, it is correct to exchange goods or services for any unit of money and it is permitted for the Muslim to sell for any currency and to buy with any currency and to hire with any currency and to be employed for any currency.