Deuteronomy 19:18
"And the judges shall make diligent inquisition: and, behold, if the witness be a false witness, and hath testified falsely against his brother;"
Cross References (ranked by relevance)
Deuteronomy 17:4
And it be told thee, and thou hast heard of it, and enquired diligently, and, behold, it be true, and the thing certain, that such abomination is wrought in Israel:
Deuteronomy 13:14
Then shalt thou enquire, and make search, and ask diligently; and, behold, if it be truth, and the thing certain, that such abomination is wrought among you;
Job 19:16
I called my servant, and he gave me no answer; I intreated him with my mouth.