to express belief? Who expresses the belief?

A religion expresses the belief of its members.

Just sounds like a poor definition to me. Where did it come from?

Many dictionaries. As a brief definition I think it's quite good. Can you suggest a better one?

I guess I haven't seen those dictionaries. Personally, I wouldn't call religion an "institution." I might call it a creed, a set of beliefs, or something like that.

P.S. I decided to look at a dictionary. The first online one I came across gives this:

: the belief in a god or in a group of gods

: an organized system of beliefs, ceremonies, and rules used to worship a god or a group of gods

: an interest, a belief, or an activity that is very important to a person or group

http://www.merriam-webster.com/dictionary/religion