2 Samuel 16:10

And the king said, What have I to do with you, ye sons of Zeruiah? Joab had probably agreed with his brother Abishai on the need of swift and drastic measures against Shimei, and David declared with great emphasis that he could not share their attitude. So let him curse, because the Lord hath said unto him, Curse David. In his humility David was willing to consider it a special dispensation on the part of God, permitting Shimei to cast such aspersions upon him. Who shall, then, say, Wherefore hast thou done so?