Nasai

(1) The Messenger of Allah (sallallahu alayhi wa sallam) purchased a camel from Jabir (radi Allahu anhu) during a journey. The price was fixed at forty dirhams. The payment was made upon arrival in Madinah Munawwarah.

(2) “He called for the scales”: In that era, dirham and dinar coins existed among the Arabs, but they were very rare; rather, transactions were generally conducted with gold and silver, which were given by weight.

(3) “He gave more”: To give someone more than their due right is a good and recommended act, even if it is in the case of a loan. It becomes usury (riba) when there is a condition for the excess, or the creditor demands it, or at the very least, desires it. If the debtor, of his own accord, gives more than the loan amount, this is a good thing, because when giving the full amount, there is a possibility of deficiency in the weighing, so he should give extra so that there remains no possibility of shortcoming. To give extra at the time of weighing is a mark of nobility.