the geneva catechism 4
202. Does it not require anything else? We must always regard the nature of the Lawgiver, who does not halt at the outward act, but requires the affection of the heart.
203. What more then does it mean? Since our bodies and our souls are temples of the Holy Spirit (1 Cor. 3:16, 6:15; 2 Cor. 6:16), we must preserve them in uprightness. And so we must be chaste not only in deed, but also in desire, word and gesture. Accordingly no part of us is to be polluted with unchastity.
204. Let us come to the eighth commandment. Thou shalt not steal.
205. Is it only meant to prohibit the thefts which are punished by justice, or does it extend further? It refers to all civil traffic and unscrupulous means of acquiring our neighbour's good, whether by violence, or fraud, or in any other kind of way that God has not allowed.
206. Is it enough to abstain from evil deeds, or is covetousness also included here? We must ever return to this, that the Lawgiver is spiritual, that He does not speak simply of outward thefts, but all schemes, wishes and plans to enrich ourselves at the expense of our neighbour.
207. What are to do then? We must do our duty in preserving for every man his own.
208. What is the ninth commandment? Thou shalt not bear false witness against thy neighbour.
209. Does it forbid perjury in court, or any kind of lying against our neighbour? In mentioning this one case it gives a general instruction, that we are not to speak evil of our neighbour falsely, nor by our slanders and lies are we do him harm in his possessions, or in his reputations.