The fourth commandment can be stated as:
Remember the Sabbath day by keeping it holy.  Six days you shall labor and do all your work, but the seventh day is a Sabbath to the Lord your God.  On it you shall not do any work, neither you, nor your manservant or maidservant, nor your animals, nor the alien within your gates.  For in six days the Lord made the heavens and the earth, the sea, and all that is in them, but he rested on the seventh day.  Therefore, the Lord blessed the Sabbath day and made it holy.  (Ex 20:8)
It is frequently held, by Christian scholars, that this commandment applies to Christians as well as Jews.  Consider the words of Samuel Wakefield:
“While, therefore, the Sabbath itself is a perpetual institution, morally binding upon all men, the law which determines the time of its observance is purely positive, and consequently may be changed…That the precise time of the Sabbath is not essential to the institution, and that this may be changed by Divine authority without making any alteration in the law of the Sabbath either as it stands in the second chapter of Genesis, or in the fourth commandment.  It is, therefore, as consistent with the nature of the institution for Christians to observe the first day of the week, as it was for Jews to observe the seventh.”
However, most Christians observe neither Saturday nor Sunday as a Sabbath.  Instead, they observe Sunday as a day of worship.  If asked to explain why, many Christians claim that, when Jesus rose from the dead, the observance of the 4th commandment was automatically changed from Saturday to Sunday and the purpose was changed from a ‘day of rest’ to a ‘day of worship.’ But curiously, there is no record in the New Testament of such a change.
Ignatius, companion of the apostles, advocated breaking away from the Sabbath:
“Let us no more Sabbatize but let us keep the Lord’s day, on which our Life arose.”
John R. Rice was even more forceful:
“Sunday is not the Sabbath.  The Bible never once speaks of it as a Sabbath.  The Bible does not command Christians to keep Sunday as a Sabbath.  In fact, the New Testament does not command Christians to keep any Sabbath whatsoever.  The Sabbath was for Jews under ceremonial law.  It was for no one else.  It was a special covenant and sign between God and the Jews.
To be sure, New Testament Christians do well to meet on the first day of the week for worship and service to God.  New Testament Christians did, as indicated in Acts 20:7 and 1 Cor 16:2.  It is called the Lord’s Day (Rev 1:10).  But the Lord’s Day is not the Sabbath day.  It is used primarily as a day of praise and service, not as a day of rest.  Its observance is voluntary and not commanded at all in the Bible.  Our Lord’s day is grace, pure and simple, not law.  We should encourage Christians everywhere to make much of the Lord’s day as a day of special privilege and blessing and worship and praise.  But never call the Lord’s day the Sabbath.  Sunday is not the Sabbath and never was.”