I know I am probably one of the last individuals to provide opinion on this but I guess you didn’t mean to but may be he took it as if you asked him out on a date? What was his body language? His facial expression? Smiling, frowning, was he charming, tense,etc?
At this moment, all I can think of is that it doesn’t matter if you actually asked him out on a date because it seems like you have a date regardless[emoji4] I guess you will know the answer of this question by the way he treats you on the actual day.
May be to take the pressure of, we call it a biking appointment with a friend[emoji4]