FROM SABBATH TO SUNDAY, THE DAY OF THE LORD

"Kuya Jeff, with reference to the third commandment, we grew up believing that Sunday "replaced" the day of the Sabbath after Jesus' resurrection. Could you please provide additional discussion on this? Initially, related results that I got from the web either (a) refutes Sunday as the day that Jesus rose from the dead or (b) states that the Bible did not explicitly intend such replacement. Thank you for understanding." ~Erwin B. 

1. Sabbath or the Saturday observance commemorated God's day of rest during the seven-day creation account of Genesis. It is one day of rest and refreshment for everyone, being mindful of the many blessings received through creation (cf. Genesis 2:2–3). Sabbath was also sacred because of what God has done for His people when He liberated them from slavery in Egypt. Thus, Sabbath is also a day of remembering the covenant He had made with His people through the Passover sacrifice and the giving of the Law at Mount Sinai (cf. Exodus 20:11; 23:12). The Sabbath was a special sign to the Israelites that they had been set apart as followers of the most High God. 

2. Interestingly enough, of the Ten Commandments listed in Exodus 20:1-17, only nine of them were restated in the New Testament. Six in Matthew 19:18 - murder, adultery, stealing, false witness, honor parents, and worshiping God; Romans 13:9 - coveting. Worshiping God properly covers the first three commandments. The one that was not reaffirmed was the one about the sabbath. Instead, Jesus said that He was Lord over the sabbath (Matthew 12:8). 

3. Our Lord Jesus Christ rose from the dead on the first day of the week which is Sunday. According to the Catechism of the Catholic Church (2174), on the one hand, because it is the "first day," the day of Christ's Resurrection recalls the first creation. On the other extreme, 
because it is the "eighth day" following the sabbath it stands for "re-creation," the Redemption. Sunday marks the day of the new creation, when Christ conquered sin, darkness and death. Sunday marks the day of the new covenant when Christ, the High Priest who offered Himself as the unblemished Passover lamb of sacrifice on the altar of the cross, gave the promise of everlasting life. Therefore, Sunday is the fulfillment of the sabbath of the Old Testament. 

4. One can find clear evidence in the New Testament that the day of the Resurrection, namely Sunday, became the day of the gathering of Christians, in worship and the Holy Eucharist: 
"On the first day of the week, when we were gathered together to break bread, Paul talked with them, intending to depart on the morrow; and he prolonged his speech until midnight." (Acts 20:7) 
"On the first day of every week, each of you is to put something aside and store it up, as he may prosper, so that contributions need not be made when I come." (1 Cor. 16:2)

5. The Jewish people who had rejected Jesus continued to worship on Saturday, the sabbath. Christians are Easter people and the people of the New Covenant. The Christians celebrated Jesus' resurrection, and this was the driving force to gather on the first day of the week. Our observance of the day of the Lord on Sunday would distinguish us from those who do not profess the Resurrection of Jesus. Those who have remained in full continuity with the Church from apostolic times know this by the evidence in the sacred scriptures and constant practice.