The attitudes of Christian and Islamic people toward merchants and trade from religions' origins until about 1500-show change over time. At first Christians were against merchants and trade and the Muslim's were more fair towards them, but then attitudes changed when trading became wide spread and merchants gained peoples respect. Which marked the acceptance of merchants.
Christians changed their point of view towards merchants only once over time. They were against merchants all the way till the end. The first document in 70-80 CE was negative and they were negative towards merchants until 1300 CE When they believed merchants had been blessed with the riches from God, and that they had fair prices and they did not have to raise their prices because they did not get a good deal, rather just not sell it at all.
In the beginning, the Islamic people on the other hand were more lenient towards merchants.
They accepted them and did not show any mistrust. Although over time they lost respect for them and later just didn't care. For example is 620-650 CE Muslims thought of merchants as great people and that they shall be blessed, but over time that changed into hatred. In 1300 they believed that merchants were greedy and dishonest. Yet in 1400 they realized that they needed the merchants to get goods.
Additional information that would be helpful to asses the consequences of the attitudes from above would be an actual letter or note from a buyer or of someone who refused to buy from them to see the point of view from someone of each religion at a certain time. Such as a letter from a Christian buyer during the fourteenth-century showing that he was glad to buy from a merchant or a letter from a Muslim during the fourteenth-century showing that they didn't want to buy from a merchant or if they did it was with a large hesitance.
As you can see the change over time has been drastic. It has basically gone from one thing to the opposite. Christians now see merchants with a positive, which at the beginning they sought of them as thieves. And Muslims went from loving merchants too not really caring that they exist.