The following is from thewestminsterstandard.org:
Q. 56. What is the reason annexed to the third commandment?
A. The reason annexed to the third commandment is, that however the breakers of this commandment may escape punishment from men, yet the Lord our God will not suffer them to escape his righteous judgment.
Q. 57. Which is the fourth commandment?
A. The fourth commandment is, Remember the Sabbath day, to keep it holy. Six days shalt thou labor, and do all thy work: but the seventh day is the Sabbath of the Lord thy God: in it thou shalt not do any work, thou, nor thy son, nor thy daughter, thy man-servant, nor thy maid-servant, nor thy cattle, nor thy stranger that is within thy gates: for in six days the Lord made heaven and earth, the sea, and all that in them is, and rested the seventh day: wherefore the Lord blessed the Sabbath-day, and hallowed it.
Q. 58. What is required in the fourth commandment?
A. 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.
Q. 59. Which day of the seven hath God appointed to be the weekly Sabbath?
A. From the beginning of the world to the resurrection of Christ, God appointed the seventh day of the week to be the weekly Sabbath; and the first day of the week, ever since, to continue to the end of the world, which is the Christian Sabbath.
Q. 60. How is the Sabbath to be sanctified?
A. The Sabbath is to be sanctified by a holy resting all that day, even from such worldly employments and recreations as are lawful on other days; and spending the whole time in the public and private exercises of God’s worship, except so much as is to be taken up in the works of necessity and mercy.
Recommended sermon: The Westminster Assembly, by Dr. Sinclair B. Ferguson