Should I give my friend shares? (I will not promote)

5 months ago, I had an idea, and since then I’ve been working on this idea, planning, designing, developing and implementing it all by myself. Now it’s a complete product ready to see the light. A background about me, I’m a tech guy, not a sales guy. So I needed help in the sales part. I got in touch with a friend of mine who’s gifted in the space of sales, having good connections, getting leads, demonstrating and convincing them to subscribe (SaaS model). He was excited about it, I asked him if he knows someone to make marketing ads for my product, he offered a friend of his could do it fee-free. And overall he’s willing to help me in the sales part. He and his brother will even handle sales in 2 different countries. All good so far. I initially offered him 20% sales commission for first annual revenue of every sale he gets me, which I believe is the reasonable rate, and he was happy with it. A few days ago, he expressed how invested he is in the idea, and how he sees a future for it, and now wants a share from it.. a small 2% portion with commissions lowered to 15%. I see great value in him, he can be very beneficial, with his connections, soft skills, sales and negotiating capabilities, offering help in marketing and operations, and exposure through him to markets of 2 other countries than where I’m originally launching. I am new to business, clueless, and I don’t want to do a stupid mistake. I know what he’s asking for is so small almost negligible (2%), but it’s a matter of principle. I keep asking myself, why would I give away a portion of what I worked on for months, alone, a portion of my own original idea? while I’m already giving him his commission for what he’s offering me? But then again, I look back at the benefits of having him with me, benefits going beyond just “sales”, like marketing, operations, connections, exposure to markets, and then I think, he’s not asking for much, so why not buy his loyalty and passion for this 2%? He would probably still be willing to work with me even if I rejected, but I fear losing his passion and excitement. How should I approach this? Is it worth it? Am I being reasonable or am I being greedy?