I have recently been asked how the Church can require us to attend Mass at the very least on Sunday. Then to go on and say if we do not attend we will have mortal sin on our soul.
The phrasing of this question shows either bias or ignorance. Like the last two posters said, the Church does not require it, God does.
Plus, the Church never says a sin is necessarily mortal. The closest we get is saying that violations of any of the Ten Commandments (which we have in this case) constitute a sin of grave matter. For it to be a mortal sin, the sin must be of grave matter. But, in addition, the sinner must have full knowledge of the gravity and full consent of the will in commiting the sin.
This raises another intersting point, or at least I find it interesting: If a person cares about whether or not they are commiting mortal sin, and believes the Church’s teaching on the nature of mortal sins has any real value, then why would they be so upset at the Church’s teaching on keeping the sabbath holy?
Also, we are not physically forced attend. Membership in Christ’s Body is voluntary, of course all should join though. We Catholics believe as the Church teaches. Only those of us who know that the Church is right have the possibility of sinning mortally, because we are the only onew who know fully of the truth of this interpretation of the commandment.
Where is these teachings backed in scripture?
You could always ask the person asking you why it *must *be backed in scripture. As in, “Which verse says that only sacred scripture canonized by both first-century Jews and fourth-century Christians indicates that such scriptures clearly contain the answers to all of your questions about God and no other sources are to be trusted?”
You could top this off with opening up your Bible to John 20:30-31 - “Now Jesus did many other signs in the presence of his disciples that are not written in this book. But these are written that you may beleive that Jesus is the Messiah, the Son of God , and that through this belief you may have life in his name.” And John 21:25 - “There are also many other things that Jesus did, but if these were to be described individually, I do not thnk the whole world would contain the books that would be written.”
Maybe it’s just where my mind always goes, but I think this question belongs in the apologetics forum, not liturgy and sacraments, which I just realized is where it happens to be

.