When someone sees and realizes true dharma / the real nature of the things around, that someone feels he or she is attaining a great bliss, peace and freedom within this realization. So he or she starts sharing these realization experiences with the others.
But telling the dharma to others can be done by many people. But most important thing is living it. While going through the path of realization, sharing it with the others is what we need to do.
Think of a person who is giving food to everyone for free, but he is not eating and feeling hungry and bearing hunger inside. So what is the point of giving out food for others while he/she is hungry. He/She is harming own self and trying to heal others. Like wise if someone is sharing all dharma verses and helping others to realize and that someone is suffering inside. What is the point.
First thing is not to believe in anything what other people say, until you truly realizes the truth within. And first we ourselves must live accordingly to dharma and then can share it with others.
People are all the time talking about what Buddha said, what Jesus said etc. But they never apply these things in to the real life. The life of Buddha, Jesus etc itself was bringing out truth.
First you need to save yourself to save others. While drowning in a stream, helping others to come out is a joke.
Look consciously, see the truth, awaken the wisdom and realize within the true nature of everything. This is the path towards complete true happiness and freedom.
Religion is something that we believe in some one else's experience. But spirituality is your own realization experience.
May everyone come out of suffering. May they have strength to eliminate all anger,lust,jellousy,sorrow and suffering. May they see truth and be happy, loving, free and full of awareness.