There is no business agreement too small to get in writing. It does not have to be drafted by attorneys, or even look formal. But putting things in writing: delivery date, price, and requested quality of the goods, is just good business practice.
It makes it clear that the parties agreed to the terms. It creates a paper trail so if things go wrong, you have something to rely on other than memories of what was said when and to whom.
While it may seem like this amount of formalization means you don’t trust your business partner, it isn’t about trust. It’s about making sure everyone agrees on the basics.