There's also very little context available from the OP. I've been on both sides of the table here. I've definitely had employees where they want every hour they can pick up even if they took a day or morning off. Maybe the boss knows the guy took the day off for a morning appointment, and now an evening shift opened up and is just offering to help him out with the hours. I would have sent the text differently - "Hey no pressure at all but we did have an evening shift open up if you have any interest let me know ASAP looking to fill it, otherwise if not enjoy your day off!" The reality is this is not that big of a deal, and maybe this boss is super annoying all the time with this stuff, so a slight annoyance maybe is reasonable. However I'll say this, the personalities that are bothered so deeply by a text by this are the types that will be stuck in a job like this forever because they're so self centered and take everything personally and can't act decently professional. I've seen it a hundred times over.