The Jews by divine mandate rested and worshipped on the seventh day of the week since this is the day on which God "rested" and ceased creating the universe.
When Christ, the King of Creation died and rose on Sunday, He instituted a "new creation." By rising on the day after the seventh day Sabbath, He fulfilled the promise of the eighth day which had been mystically represented in the Old Testament sacrament of circumcision (Jewish boys were circumcised on the eighth day). So then, this eighth day mystically stands outside the weekly cycle. Moreover, the Holy Spirit descended upon the Church on a Sunday and this gave even more significance to Sunday worship.
The Apostles and early Christians celebrated the Holy Eucharist daily, but the obligation of attending the Eucharistic liturgy on Sunday was required since the moral precepts of Ten Commandments were not abrogated by Christ. Christians continued to worship and rest one day out of seven days - but Sunday was the now the "Sabbath day" of the New Testament.
Take for example the words of Saint Ignatius (died ca. AD 108) to the Magnesians:
We have seen how former adherents of the ancient customs have since attained to a new hope; so that they have given up keeping the sabbath, and now order their lives by the Lord's Day instead, the day when life first dawned for us, thanks to Him and His death.
I could cite literally hundreds of passages from the Church Fathers on this topic. Let it suffice that Sunday was universally the day of obligatory worship and rest.
Regrettably, Catholics have forgotten the obligation to rest from labor on Sundays. Rest on Sunday is still taught by the Catholic magisterium. For example, Blessed John Paul II's apostolic letter Dies Domini (On keeping the Lord's day holy) teaches Catholics the moral obligation of keeping Sunday holy through rest, recreation, and attendance at Holy Mass. He also urges Catholics to resist the "weekend mentality" in which Sunday becomes blended into a time of either labor or frivolous amusements.
Many of the great saints and many of Our Lady's messages have stressed the necessity of resting on Sunday and attending Mass on Sunday. As has always been taught, to purposefully miss Holy Mass is a mortal sin because it is very grave. Why is it grave? It is grave because we need grace more than we need food, water, and even air. Sanctifying grace is needed if we are to attain to our divinely ordered end - beatific communion with God forever.
ad Jesum per Mariam,