Deuteronomy 17:4

4.Then three shalt inquire (307) diligently. Although this moderation here refers only to the present matter, yet should it always be maintained in judicial proceedings, lest innocent persons should be treated with undue severity. Again, we must remember what I have said elsewhere, that judges are here not only restrained from precipitate condemnation, but also stimulated to beware of passing over, in idleness or negligence, anything that was necessary to be known. For they often fail in their duty, because they wilfully connive at guilt; and thus that which would be manifest if they would be at the pains to make more diligent inquiry, does not come to light. God, then, would not have them slumber nor take no notice of sinister reports, but rather inquire diligently as to things which may have come to their cars, so that no crime may remain unpunished. The same is the case as to witnesses; for whilst it would be unjust to pronounce sentence on the testimony of one man, still, if two or three will not suffice, there would be no end to litigation. Fitly, then, has God prescribed to judges both that they shall not be rashly credulous, and yet that they shall be content with the lawful number of witnesses; but this point will be more largely treated of elsewhere in commenting both on the Sixth and Ninth Commandments.