In a brief but complete article written on a Saturday, entitled, Why Do We Worship on Sunday? [dead link removed] Patrick of Patrick’s Pensees closes off saying:
Sunday, not Saturday, is the Christian Sabbath. To continue to observe the fourth commandment on the last day of the week is to deny, by implication, the coming of Christ and his once and for all redemptive work. On the other hand, observing Sunday testifies to the fact that Christ has conquered sin and death so that whoever believes in Him should not perish but have everlasting life.