Don't speak in a way that causes pain for others, either by making pointed remarks and exposing their faults or, in the case of nonhuman beings, by using mantras that drain their life.
From The Great Path of Awakening : An Easily Accessible Introduction for Ordinary People by Jamgon Kongtrul, translated by Ken McLeod. Copyright 1993 by Ken McLeod.
Published by arrangement with Shambhala Publications, Inc., Boston.
This site provides an on-line database of commentaries on the Tibetan Buddhist meditation practices of lojong (Mind Training) and tonglen.