Q. What are the reasons annexed to the second commandment, the more to enforce it?
A. The reasons annexed to the second commandment, the more to enforce it, contained in these words, For I the Lord thy God am a jealous God, visiting the iniquity of the fathers upon the children unto the third and fourth generation of them that hate me; and showing mercy unto thousands of them that love me, and keep my commandments; are, besides Godâ€™s sovereignty over us, and propriety in us, his fervent zeal for his own worship, and his revengeful indignation against all false worship, as being a spiritual whoredom; accounting the breakers of this commandment such as hate him, and threatening to punish them unto divers generations; and esteeming the observers of it such as love him and keep his commandments, and promising mercy to them unto many generations.
Q. Which is the third commandment?
A. The third commandment is, Thou shalt not take the name of the Lord thy God in vain: for the Lord will not hold him guiltless that taketh his name in vain.
Q. What is required in the third commandment?
A. The third commandment requires, That the name of God, his titles, attributes, ordinances, the Word, sacraments, prayer, oaths, vows, lots, his works, and whatsoever else there is whereby he makes himself known, be holily and reverently used in thought, meditation, word, and writing; by an holy profession, and answerable conversation, to the glory of God, and the good of ourselves, and others.
(Questions CX, CXI and CXII of the Westminster Larger Catechism.)