Assuring when assurance doesn't help

"One thing about my checks. They're always good."
That might be the worst sentence I hear in sales. And it was spoken to me a few minutes ago as I was given a significant check.
Maybe I'm just paranoid. I have no actual reason to suspect the check is not good. The man who gave it to me has been a customer for around 10 years. Yet before today he always paid cash (which is certainly nice) or with a credit card (which of course I could run immediately). Then this morning he gives me his first check, and his reassurance was not reassuring.
It seems as though every time myself or Pops before me heard those or similar words we'd have trouble with the check which was always good. Oh, I'm sure not every time. But admit it, when a body has to make it a point to tell you their check is good it actually makes it suspect. I had already agreed, on my admittedly unspoken word, that I trust his check. After that point, why must he assure me it's good? He even went to the point of showing me that his address was on the check. O-kay. Why would I not expect that?
I was sure the check was good. But I ran it down to the bank right away just the same.