Sounds like you handled his remark pretty well by just walking away..he didn't get the reaction he was looking for. I don't know the details of all this of course, and am not asking that you give them if you'd rather not. If he is someone who continually makes snide remarks, and that is causing a regular work issue, then talk to someone over his head. Chances are you wouldn't be the first person to call him on this. If he was making a snide comment in response to your having a bad day last week, but is normally okay to work with, then you will need to decide which way you want to go with that. Glad you decided to face it head on today and go in to work. That was the hardest part, and you made it through the day.