Q. 71 What is required in the seventh commandment? A. The seventh commandment requireth the preservation of our own and our neighbour's chastity in heart, speech, and behaviour. Q. 72 What is forbidden in the seventh commandment? A. The seventh commandment forbiddeth all unchaste thoughts, words, and actions. Today, we will look at the place that sex has in the three-fold purpose of marriage. Remember that marriage is the only place where sexual expression is allowed. God will judge us if we engage in it elsewhere (Heb 13:4). So as marriage is the only relationship that is meant to be sexual, it is very important for us to understand the place that sex has in marriage.