Charles Ellicott Commentary 2 Samuel 16:10

"And the king said, What have I to do with you, ye sons of Zeruiah? Because he curseth, and because Jehovah hath said unto him, Curse David; who then shall say, Wherefore hast thou done so?" — 2 Samuel 16:10 (ASV)

So let him curse. — This translation follows the margin of the Hebrew, as the Septuagint and Vulgate also do. David, throughout, recognizes that all his sufferings were from the Lord's hand, and he wishes to submit himself entirely to His will. He does not, of course, mean to justify Shimei's wrong; but only to say that, as far as Shimei's sin bears upon David himself, it is of Divine appointment, and he cannot resent it.