Apollodorus Against Stephanus, Charged with False Testimony II (6)

And surely, if he says that he believed this to be true because Phormio said it was, it would be like the same man to believe him when he said this, and to testify to it at his bidding. The laws, however, do not say this, but ordain that a man may testify to what he knows, or to matters at the doing of which he was present, and that his testimony must be committed to writing in order that it may not be possible to subtract anything from what is written, or to add anything to it.