John Gill Commentary Exodus 20:16

"Thou shalt not bear false witness against thy neighbor." — Exodus 20:16 (ASV)

You shall not bear false witness against your neighbour .
Neither publicly in a court of judicature, by laying things to his charge that are false, and swearing to them, to his hurt and damage; nor privately, by whispering, tale bearing, backbiting, slandering, by telling lies of him, traducing his character by innuendos, sly insinuations, and evil suggestions, whereby he may suffer in his character, credit, and reputation, and in his trade and business.

Aben Ezra thinks the words describe the character of the person that is not to bear witness in any court, and to be read thus, "you shall not answer who are a false witness": or, "O you false witness": meaning that such a one should not be admitted an evidence in court, who had been convicted already of being a false witness; his word and oath are not to be taken, nor should any questions be put to him, or he suffered to answer to any; his depositions should have no weight with those before whom they were made, nay, even they should not be taken, nor such a person be allowed to make any; but this is to put this precept in a quite different form from all the rest, and without any necessity, since the word may as well be taken for a testimony bore, as for the person that bears it. This is the ninth commandment.