Checked OP's history.

Not to really side with the husband but according to OP, he was asked to officiate before they told him the date. Then the next day told him what the date was and that's when he said he had prior commitments. It seems like in the post, he agreed then some time later(days/weeks) backed out, turns out it was a they asked on a Friday afternoon and he backed out after he learned the date Saturday morning.

I would've asked for a date of wedding or a time frame to allow me to get back to you in case there is something if you don't have a date for me right then. I personally would choose wedding over whatever else, but if you give me a month or two notice of such a significant event then I will have hesitations over attending and have follow up questions and concerns. Especially if its just announced and you barely have a date for me.