2 Samuel 16:5-7, 9-10

And when king David came to Bahurim, behold, thence came out a man of the family of the house of Saul, whose name was Shimei, the son of Gera: he came forth, and cursed still as he came. And he cast stones at David, and at all the servants of king David: and all the people and all the mighty men were on his right hand and on his left. And thus said Shimei when he cursed, Come out, come out, thou bloody man, and thou man of Belial

Then said Abishai the son of Zeruiah unto the king, Why should this dead dog curse my lord the king? let me go over, I pray thee, and take off his head. And the king said, What have I to do with you, ye sons of Zeruiah? so let him curse, because the LORD hath said unto him, Curse David. Who shall then say, Wherefore hast thou done so?