“Kind Speech” means, when meeting with living beings, first of all to feel compassion for them and to offer caring and loving words.
Broadly, it is there being no rude or bad words. In secular societies there are polite words “take good care of yourself!” and there is the disciple’s greeting”how are you?” Speaking with the feeling of “compassion for living beings as if they were babies” is kind speech. We should praise those who have virtue and should pity those who lack virtue. Through love of kind speech, kind speech is gradually nurtured. Thus, kind speech which is ordinarily neither recognized nor experienced manifests itself before us. While the present body and life exists we should enjoy kind speech, and we should not regress or deviate through many ages and many lives. Weather in defeating adversaries or in promoting harmony among gentlefolk, kind speech is fundamental. To hear kind speech indirectly etched an impression in the heart and in the soul. Remember, kind speech arises from a loving mind, and the seed of a loving mind is compassion. We should learn that kind speech has the power to turn around the heavens; it is not merely the praise of ability.
-excerpt from: Shobogenzo, Bodisatta-shishobo- Master Dogen-
Translated by Master Gudo Wafu Nishijima and Chodo Cross