How many religions have to marry within the religion?

Many religions have laws against marrying outside of their beliefs in order to preserve their ideals and community. All religions need a strong believing youth in order to preserve the religion's tradition and teachings. When nonbelievers marry in, the structure of the family can be tainted because each parents has different teachings they may want to teach their kids. Religions find importance in raising children and youth to believe in their faith so that the future is upheld and the family is more likely to remain intact.

However, this does not mean many religions are against others. Most religions are accepting of others and understand that different people may believe different things. Some religions allow marrying outside of the faith but, require the religious parent to raise their children in the faith.