Herein someone avoids lying and abstains from it. He speaks the truth, is devoted to the truth, reliable, worthy of confidence, not a deceiver of men. Being at a meeting, or amongst people, or in the midst of his relatives, or in a society, or in the king’s court, and called upon and asked as witness to tell what he knows, he answers, if he knows nothing: ‘I know nothing’, and if he knows, he answers: ‘I know’; if he has seen nothing, he answers: ‘I have seen nothing’, and if he has seen, he answers: ‘I have seen’. Thus he never knowingly speaks a lie, either for the sake of his own advantage, or for the sake of another person’s advantage, or for the sake of any advantage whatsoever.
He avoids tale-bearing, and abstains from it. What he has heard here, he does not repeat there, so as to cause dissension there; and what he has heard there, he does not repeat here, so as to cause dissension here. Thus he unites those that are divided; and those that are united, he encourages. Concord gladdens him, he delights and rejoices in concord; and it is concord that he spreads by his words.
He avoids harsh language, and abstains from it. He speaks such words as are gentle, soothing to the ear, loving, such words as go to the heart, and are courteous, friendly, and agreeable to many.
He avoids vain talk, and abstains from it. He speaks at the right time, in accordance with facts, speaks what is useful, speaks of the law and the discipline: his speech is like a treasure, uttered at the right moment, accompanied by arguments, moderate and full of sense.
This is called Right Speech."
(Buddha, Anguttara Nikaya 10.176)