From the Kakacupama Sutta:

"Monks, there are these five modes of speech which people might use when speaking to you — speech that is timely or untimely, true or false, gentle or harsh, with a good or a harmful motive, and with a loving heart or hostility.

"Monks, some might speak to you using speech that is timely or untimely; monks, some might speak to you according to truth or falsely; monks, some might speak to you gently or harshly; monks, some might speak to you with a good motive or with a harmful motive; monks, some might speak to you with a loving heart or with hostility. On all occasions, monks, you should train yourselves thus: 'Neither shall our minds be affected by this, nor for this matter shall we give vent to evil words, but we shall remain full of concern and pity, with a mind of love, and we shall not give in to hatred. On the contrary, we shall live projecting thoughts of universal love to that very person, making him as well as the whole world the object of our thoughts of universal love — thoughts that have grown great, exalted and measureless. We shall dwell radiating these thoughts which are void of hostility and ill will.' It is in this way, monks, that you should train yourselves.

"Suppose, monks, a person were to come to you, holding a hoe and a basket and he were to say: 'I shall make this great earth earthless.' Then he would strew the earth here and there, spit here and there, and urinate here and there, and would say:' 'Be earthless, be earthless.' What do you think, monks, would this person render this great earth earthless?"
"No, indeed not, most venerable sir."

"And why?"

"Because this great earth, most venerable sir, is deep and without measure. It cannot possibly be turned earthless. On the contrary, that person would only reap weariness and frustration."
"In the same way, monks, others may use these five modes of speech when speaking to you — speech that is timely or untimely, true or false, gentle or harsh, with a good or a harmful motive, and with a loving heart or hostility. In this way, monks, you should train yourselves: 'Neither shall our minds be affected by this, nor for this matter shall we give vent to evil words, but we shall remain full of concern and pity, with a mind of love, and we shall not give in to hatred. On the contrary, we shall live projecting thoughts of universal love to that very person, making him as well as the whole world the object of our thoughts of universal love — thoughts that have grown great, exalted and measureless. We shall dwell radiating these thoughts which are void of hostility and ill will.' It is in this way, monks, that you should train yourselves.