Adam Clarke on 2 Samuel 9:11

So shall thy servant do - The promises of Ziba were fair and specious, but he was a traitor in his heart, as we shall see in the rebellion of Absalom, and David's indulgence to this man is a blot in his character; at this time however he suspected no evil; circumstances alone can develope the human character. The internal villain can be known only when circumstances occur which can call his propensities into action; till then he may be reputed an honest man.