Is it a sin to tell people wrong things without knowing about them?

Dear Brother / Sister,

This issue has two aspects:

1. If a person who is an expert in religion tells people something wrong by mistake, he is not held responsible.

2. If a person who is not an expert in religion tells people something wrong by mistake, he is held responsible because it is not appropriate for a person to talk about something that he does not know.  

For instance, if an electrician makes a mistake while repairing an electrical device, he will not be held responsible. For, he has done his job. He has not made that mistake deliberately. However, a person who is not an electrician makes that mistake, he will be held responsible because has done it though he is not good at it.

Similarly, a person who is not an expert in religious issues may make a mistake when he speaks about religion; since he speaks though he is not very good at religious issues, he will be held responsible.

Questions on Islam