Are you in the USA?
Are you getting a true commission, as in a percentage of the sale or contract value or are you just getting a bonus / referral / finder's fee?
Commissions are not normal for consultants at consulting shops or services companies, at least in the States. Sometimes it is possible to strike a one off deal with a sales team to get a bonus, but definitely not a commission.
Have both been a consultant and sold consulting services, now I'm at a product company doing presales. At consulting shops it's normal for consultants to get a straight salary and then a bonus for hitting a certain billable hour % or total hours for some period (like monthly, quarterly, etc).
There are these things called SPIFFs, basically a bonus for doing something specific, such as demoing a certain product, installing a product with a new feature, etc that consultants sometimes can qualify for. But again, straight commission is not normal. If you find a place that does, it might be a good place to stay!
Unless, they give you a quota then guess what... you aren't a consultant, you are an SE.
I assume you are a consultant at this new place? Relationships are how sales are won. These other people saying it is fishy are not giving you objective advice, this is absolutely normal. Have you never asked someone else for an introduction, reference, or info about to another person or company? This is the same thing.
Depending on how it was communicated to you and that person's personality may have made it seem like a requirement, which it is not. But it is probably a good idea to help for several reasons:
It helps the company increase sales which means they stay alive.
Improves the likelyhood of you having a project.
You, hopefully, are working for a company that has a product(s) which solves business needs, so you would be helping both your contact's company and yours.
It improves your relationship with your original contact and the sales team.
Gives you an opportunity to try some light sales skills, something you may be interested in the future.
I am southern and raised to always be respectful and refuse to sell my soul. With that, you should never feel required to do an introduction or push a product/service when that is not your job or you do not feel it is appropriate. Somes sales people may not like this, but fuck them and their boats.
Feel free to reach out if you want to chat more. I have been working on a sales engineer book which includes information similar to these situations. I'll share it when done.
Good luck!