Why is Missing Sunday Mass Considered a Sin?

I’ve been asked this question many times before. To answer it, one has to understand the mass. It is a reliving of the sacrifice of Jesus in Calvary. In doing so, we also commemorate the sacrifice he made to “save” us. Let’s draw an analogy. Suppose your father fought during WWII and died in the war. It’s only proper to honor the sacrifice he made to “save” you from fascism. If you refuse to go to his memorial service, then this would be a grave insult. Refusal to commemorate the sacrifice he made would send the message that you don’t care that he died for you. It further implies that what he did was not important to you. How do you think his dad, your grandfather, would feel about that? I think he would be deeply hurt and offended by it. So ask yourself, how do you think God the Father would feel, if you refuse to commemorate the fact that His Son Jesus gave His life to “save” you from eternal damnation? Do you now see why it’s considered a serious offense to deliberately miss Sunday mass without any legitimate reason?