Why Go to Mass on Sunday?

Why Sunday?  God created seven days in the first two chapters of Scripture; He worked on six of them and rested on the seventh. This rest of God is the origin of the Jewish Sabbath.  God rests, and He wants us to enter into His rest.  He desires this so much that it was spelled out explicitly in the Ten Commandments that Moses received on Mount Sinai (Ex 20:8-11).  Throughout the Old Testament God had a lot more to say about the Sabbath, and the consequences of not keeping it, of not entering into His rest with Him.  In the New Testament, the Christians began to keep Sunday, or the Lord’s day (Rev 1:10), as the day of rest.  This is the day of resurrection, the first day of the week for Christians.
 
The importance of Sunday for Christians as a day of rest and worship together was beautifully explained in the Second Vatican Council: “By a tradition handed down from the apostles which took its origin from the very day of Christ's resurrection, the Church celebrates the paschal mystery every eighth day; with good reason this, then, bears the name of the Lord's day or Sunday. For on this day Christ's faithful are bound to come together into one place so that; by hearing the word of God and taking part in the eucharist, they may call to mind the passion, the resurrection and the glorification of the Lord Jesus, and may thank God who ‘has begotten them again, through the resurrection of Jesus Christ from the dead, unto a living hope’ (1 Pet. 1:3). Hence the Lord's day is the original feast day, and it should be proposed to the piety of the faithful and taught to them so that it may become in fact a day of joy and of freedom from work” (SC 106).