From Scripture we know that's Christ did not abide by the Fourth Commandment according to Jewish Law. It was on the Sabbath that Christ did most of His miracles. Neither did the Appostles abide by this Law as we know they plucked and ate ears of corn on this day. Christ made a new covenant though His Crucifixion and the example of His life, instructing us to no longer observe the day of the Sabbath as a religious observance. If you examine the New Testament you will find that all the commandments of the Decalogue are taught by Jesus or His Apostles except for the fourth one regarding the observation of the Sabbath. You cannot find one reference to the fourth commandment in the New Testament. In addition we know that Jesus condensed all the commandments into two, love of God and love of our neighbor saying, "On these two commandments hang all the Law and Prophets." (Mt 22:40) Paul we know taught day and night every day toiling in his work for the benefit of souls.
From the earliest days Christians honored the eighth day as the Lord's day, not the Sabbath. This was seen as the day of the Resurrection, a day where it was declared that we have been freed from the chains of sin and death and promised that we too will rise from bodily death into eternal life.
Elder Clopas reports the following:
On the first day of the week the event of the Resurrection took place, and on the first day of the week in Emmaus He performed the first Liturgy with the breaking of bread before His disciples. It was on the evening of the first day of the week, "when the doors wre shut where the disciples we assembled for fear of the Jews, Jesus came and stood in the midst of His disciples and said to them, "Peace be unto you." It was on the first day of the week (Sunday) that the Savior breathed on His disciples giving them the power to bind and loose the sins of men. On the same day of the week, as well, He appeared to His disciples again, with Thomas present, for whom He fortified his faith in His Resurrection. In addition, it was on this day that the Apostles celebrated the breaking of bread, in other words, the Divine Liturgy. On the same day the gathering of economic aid and preaching as organized by the Apostles took place in order to assist the impoverished Christians.
In this way the Resurrection day (Kyriaki - Sunday) became from the earliest times the day of the Divine Liturgy. We can see this in the writings of early Church Fathers.
Saint Ignatius writes,
Those who we brought up in the ancient order of things have come to possession of a new hope, no longer observing the Sabbath, but living in the observation of the Lord's Day...
Saint Justin Martyr writes,
Sunday is the day on which we all hold our common assembly, because it is the first day on which God, having wrought a change in the darkness and matter, made the world; and Jesus Christ our Savior on the same day rose from the dead.
Elder Cleopas tell us,
"We can find similar testimonies in the Didache (or Teaching of the Twelve Apostles), in the canons and the multitude of the holy Fathers and writers of the Church from the second to the fourth century, as for example Tertullian, Saint Irenaeus, Saint Ambrose, Saint John Chrysostom and many others. In fifth century, Sunday became a secular day of rest by a decree of Constantine the Great which affirmed the general practice of Chrstians at that time.
Reference: The Truth of Faith, pp 169 - 191
