I have a question, please don't take it as an offense, and maybe I misunderstood.

I was watching the livestream of a Persian Sheikh because though I'm not a muslim I enjoy listening to monotheistic wisdom and programs of the 3 religions. While watching livestream by the Persian Sheikh, I found the discussion fascinating as it delved into the concept of purity and impurity in various aspects, including food (halal/haram) and the reasons behind prohibitions like those concerning pigs and dogs and alcohol, which I could relate to. However, the Sheikh went on to talk about the distinction between pure and impure people, stating as an example that Muslims can eat bread prepared by Christians or Jews but not by Hindus or Buddhists. He was not mean or anything but he was talking about this concept that people that are polytheistic are impure, and made feel weird about it. I'm curious about the origins of this concept. Is it derived from the Quran? Additionally, I wonder if this concept might vary in other Islamic traditions, such as Sunni Islam, because the Sheikh was Iranian and I think it's a little different. (Excuse my English, I'm still taking classes)