The Westminster Puritans answered the question thusly:
This commandment is different than the other nine, because at no time in the New Testament is the Christian commanded to keep the sabbath day. All other nine commandments are expressed in the New Testament but the keeping of the sabbath is not.The fourth commandment requireth the keeping holy to God such set times as he hath appointed in his word; expressly one whole day in seven, to be a holy sabbath to himself.
What is the sabbath? The sabbath is an every seventh day rest from labor in honor of the God of Israel. The first time that the sabbath is mentioned in Scripture is Genesis 2:1-3. As God’s covenant people, He began to form their lives in the pattern of seven days. Working six days and resting on the seventh. In the Mosaic covenant, the sabbath was connected with the gathering of manna. (cf. Exodus 16)
All of scripture points to Christ, so how should the Christian understand this commandment? What is really required in the fourth commandment? The fourth commandment requires trust in God. The Israelite was to trust that God would provide for his needs on the seventh day despite not working on it. The Christian is to trust that all of our righteous needs are provided for in Jesus Christ alone.
Your Servant for Jesus’ Sake