You are in Sales,One of your colleague who is performing badly is requesting you to give him important sales leads or customers at your cost Your Say?

It depends on why this colleague performing badly!

But aby way must give a hand by leading or advising through the sales process.

First thing you should keep in the mind that he is your friend. The most important thing is that, this is your duty to make or show him the correct way i.e. by convincing or guiding him to be truly good towards the company.