Why is spain a good example of how most conquered peoples of other faiths were treated under the umayyads caliphate

During the Umayyad rule of the Iberian peninsula (711-1031), the society was formed by different religious groups who lived together, generally in peaceful coexistence. This was due to the fact that the large minorities of Christians and Jews were legally considered as Dhimmis, which means they were protected people and, therefore, were able to maintain their religion, their costumes and their legal system within their communities. Also, Dhimmis were required to pay the Jizya, a special tax for non-Muslims. This consideration of Christians and Jews comes from the perception in Islam that they are "people of the book," it means religions linked to Islam for their common Abrahamic origins and monotheistic belief. This tolerant policy allowed Jewish and Christian communities to thrive and were able to work in commerce, industry, and to study sciences like medicine and philosophy at the service of the Caliphate.

the constitution gives congress the power to regulate commerce "among" the several states.

where's the