A Muslim should submit to and express satisfaction with the rulings of Allah (Glorified be He), even if he does not know the reason for an obligation or prohibition. However, in some rulings the reason for a prohibition is emphatically evident as in the case of Riba. Riba entails unjustly taking advantage of the poor's circumstances and increasing their debt, not to mention the enmity and hatred it creates. Furthermore, dealing in Riba paves the way to abandoning lawful means of earning a living and solely relying on profits that come from usury in addition to other harms and evil consequences.
May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.