To attend Sunday Mass is a day of obligation for all Catholics; in fact the third commandment refers to this (Exodus 20:8-11). Jesus was faithfully observing this when He entered the synagogue on the Sabbath day.
How about us? Are we faithful to our Sunday obligation? Do we make ourselves ready for Mass by having prior knowledge of the readings specially the gospel?
Let us always remember that it is mortal sin to intentionally miss out Holy Mass on Sunday or Holy Day of Obligation, as the Church has always taught us.