It can be insult for other person if you didn't explain them why you said no to him.They can take this personally and they can do this with you same way when you were in need.So you have to know how to say them no here are some steps to say no in a proper way:
1.Be polite with your words.
2.Be firm.
3.let them know as soon as possible.
4.Be honest.
Here's the key points which you have to follow while saying no.
.jpeg&w=640&q=75)