The Forty-third Lord’s Day

43 The Forty-third Lord’s Day 
Exodus 20:18
You shall not bear false witness against your neighbour.
In this Commandment is handled the testimony of one given on behalf of another, to obtain belief or trust in them. This then is also among the things that belong to our neighbour. For it either tends to his good, or to his hurt, as the belief that is given to this testimony may either do him good, or do him harm. God in this Commandment therefore shows us not only that we should not hurt our neighbour in his honour, or life, or chastity, or goods, but also that no effectual occasion should be given for harm to him, either by words or by witnessing. Even though he might not be immediately hurt by it, he would still be hurt either by coming between his own or someone else’s credit or endeavor. The general sin that is forbidden here is called false witnessing; that is, whenever by our credit, authority, or testimony, we confirm as truth that which we know to be false, which is the very nature and definition of a lie.
Doctrine 1. Every lie, with whatever pretense it may be excused, because it is a witnessing of falsehood, it is a sin.
Reason 1. Because it contains an injury to our neighbour, who from the very law of nature has this right, that he may challenge us to say nothing to him as being true, that is not true; no more than we would foist upon him a piece of false coin as being true coin, or as being gold or silver currency, when it is only a counterfeit.
Reason 2. Because there is a base and dishonest disorder in the false witness, that lies while his tongue and speech quite disagree from his mind;1 it is as if the Interpreter of some Prince were to speak things quite contrary to those that he was commissioned by his Prince to declare.
Reason 3. Because the inconveniences that are brought forth and furthered in the world by lies are very grievous and heavy; because by these lies all trust, in which the very knot and foundation of human society lies, is troubled in every kind. There is no evil that is done to anyone, in any other way, but that it both may and usually is brought about by lies. So that by lies, sin is committed against the honour, the life, the chastity, and the outward goods of men, just as it is committed against his religion. So that, by breaking this Commandment, all the foregoing Commandments may also be broken in some way.2
Reason 4 . Because by a lie, the nature of the Devil himself is followed in a special manner, and as it were, put on like a garment. John 8:44, You are of your Father the Devil, and the lusts of your father you will do. He was a murderer from the beginning, and did not abide in the truth, because there is no truth in him. When he speaks a lie, he speaks his own: for he is a liar, and the Father of it.
1 That is, from what he knows in his mind to be true. 
2 James 2:10.
Use . Of Admonition: that out of conscience towards God, we keep ourselves from all lying, whether it is that of a pernicious lie, or an officious lie, or a merry lie.1 Whether it is spoken of ourselves, as in our vaunting and dissimulations,2 or of others, as in calumnies,3 slanders, backbitings, flatteries, soothings,4 etc. But these lies are chiefly to be shunned, as used to be committed in public judgments, and in matters of great weight and importance. 1. Because by how much advisedness5 a man lies, by so much his sin is the greater. 2. Because by how much greater the danger that another is brought into by the lie, by so much the sin is the heavier. 3. By how much greater the obligations come together that bind us to the truth, by so much the sin is multiplied.
And that we may abstain from lying, we must abstain from those things that make way for lying — such as rash suspicions, and too great an easiness to believe and receive false reports; and a talkative and twattling6 nature, which used to be exercised by so many, without that consideration whereby they should always put a difference between truth and falsehood, and the like.
Doctrine 2. We ought to love truth, and accordingly, as occasion serves, we ought to further and advance it.
This is gathered from the words of the Commandment; because veracity, whereby we both love truth, and according to occasion, witness to the truth, is that virtue commanded here; and it is contrary to that sin that is condemned here, in bearing false witness. So that speculative truth is not properly treated here, nor that which is true generally; but only moral truth — that is, what belongs to men’s manners and consciences. And that is such a truth of our words, as that they agree with our mind; and our mind also agrees with the thing itself, as far as we are bound to know, or profess that we know. And this veracity is to be followed and highly prized for these reasons:
Reason 1 . Because it is not the least part of that image of God that we ought to show, because in a special way, God is and is called the God of Truth, Psalms 31:5; and his word is called the word of truth,7 and truth itself.8 So that truth has a unique agreement with the nature and perfection of God. This is also why it is that God, though in other commands has sometimes used a kind of exception, and as it were, dispensed with it for a time, as in the matter of Theft with the Israelites (for he made it not to be a theft, by a special explication of the command, which otherwise would have been theft); and some marriages both before and under the Law, were made lawful by an extraordinary approving of them.9 Yet in this command about speaking truth, God never granted any explication or dispensation, because from the very nature of the thing itself, it has more of God’s image in it, and of his divine and immutable justice. Indeed, what is more, God has absolutely forbidden us to lie even for his cause, much less for our own or for any mortal man’s.
1 A lie said in fun, just to see what might happen. 
2 That is, “as in boasting and deceiving”.
3 A false accusation of an offense or a malicious misrepresentation of someone's words or actions. Also, an abusive attack on a person's character or good name.
4 For example, telling a lie to make someone feel better or to avoid giving offense.
5 Careful prior consideration; willful intent.
6 To talk in a digressive or long-winded way; idle talk; ill-considered speech. 
7 For example 2 Timothy 2:15; James 1:18.
8 Psalms 119:160; John 17:17.
9 No reference is given.
Reason 2 . Because this veracity is a special perfection of man, to the extent it excludes these deviations and the crookedness of men’s minds, whereby men are perverted to a habit of lying, and subjected to the base affections either of fear, or fraud, or the like. Hence also, from the very light of nature, it is a singular honour to anyone if they are lovers of truth, and stick fast to it, and are constant both in defending and furthering the truth.
Reason 3. This is also the foundation of all civil society and conversation; so that it being taken away, men would become Wolves and Foxes to one another, rather than men.
Reason 4. By the exercise and love of truth, our minds are better disposed to embrace that truth which leads to our salvation.
Use . Of Direction: that in our conversation with men, we follow after this truth. For though it is not required either that we know all that is true, nor that at all times we speak what we know to be true, yet we are never to witness anything against the truth — at no time, in no place, for no party whatsoever, not even for God himself (as was said). Moreover, we are always bound to give witness to the truth, and to confirm it when either religion or conscience towards God, or justice and charity towards our neighbour, shall require this duty from us.