To bear testimony or witness for the truth is good, but to bear false witness or to give false testimony against another is a sin against God and man.

Read for today Deuteronomy 19 through 22.

One witness shall not rise up against a man for any iniquity, or for any sin, in any sin that he sinneth: at the mouth of two witnesses, or at the mouth of three witnesses, shall the matter be established.  If a false witness rise up against any man to testify against him that which is wrong; then both the men, between whom the controversy is, shall stand before the LORD, before the priests and the judges, which shall be in those days; and the judges shall make diligent inquisition: and, behold, if the witness be a false witness, and hath testified falsely against his brother; then shall ye do unto him, as he had thought to have done unto his brother: so shalt thou put the evil away from among you.  And those which remain shall hear, and fear, and shall henceforth commit no more any such evil among you.  And thine eye shall not pity; but life shall go for life, eye for eye, tooth for tooth, hand for hand, foot for foot.
Deuteronomy 19:15-21