When Prophet Muhammad, peace be upon him came, he prohibited addition of interests to any loan so people won't be able to take advantage of each others. This is all beautiful and still valid today and will always be valid if we're dealing with each others on one to one or personal level.
For instance, if I lend you 1,000 dollars, then according to Islam, it is totally sinful for me to take advantage of you and have you sign an agreement saying that you will return 1,500 to me with in let's say 1 year. Taking interest from personal loans is what Islam prohibited.
I cant find the actual document , i am still looking, however this explains why muslims get breaks of not having to pay intrest, obama created legislation that supports and allows for this to take place as to not piss off muslims it was signed in nov or oct of 09. So imagina all the money that you pay on top of the principal note of your house, muslims dont have to is that not bias... and muslims are the only ones that recieve this , i am still looking for the official document but this should suffice