Certainly the Second Commandment obliges that we keep holy the Lord’s day. In the Old Law this mean the Sabbath, Saturday. With the New Covenant, established by Christ’s passion and death, Christians celebrated Sunday as the day of the Resurrection.
The original Catholic Encyclopedia states that during the first three centuries both practice and tradition consecrated Sunday to the public worship of God by attending Mass and resting from work. With the opening of the fourth century positive legislation, both ecclesiastical and civil, began to make these duties more definite. For more, see:
DISCLAIMER: Catholic Answers has turned over the archive to Catholic-Questions.org and no longer owns, manages, or moderates the forums. For additional apologetics resources please visit www.catholic.com.