It's from a movie about the life of Wing Chun kung fu master Ip Man, who was also one of the Bruce Lee's martial arts teachers.
Background of the line: Another kung fu master goes to master Ip's house and requests the latter to have a match with him. The line goes like this:
Challenger: So you don't want to have a match with me.
Ip Man: No. It's just that you come at a wrong time as my family and I are having dinner right now.
Ip continued: What about you? Have you eaten yet?
Ip: Then why don't you join us?
Now that's real Martial Spirit right there!