The term social cohesion refers to those things which hold a society together. A society can cohere due to things like shared ethnicity, for example. Religious traditions can also help to tie a society together by reinforcing a feeling of unity in its people.
Rituals and traditions are very important for creating cohesion. One can see this in the importance of family traditions, but one can also see it in whole societies. American society, for example, is held together in part by shared experiences such as 4th of July fireworks displays.
Religious traditions can play a similar role. When most Americans celebrate Christmas, for example, we are confirming that we share a common heritage. This helps to bind us together as a people.
Religious traditions help remind us of what we all share. By doing this, they help to bind us together.