Thomas Jefferson used the phrase "wolf by the ear" several times:
But, as it is, we have the wolf by the ear, and we can neither hold him, nor safely let him go. Justice is in one scale, and self-preservation in the other. - Jefferson to John Holmes, (discussing slavery and the Missouri question), April 22, 18201
[W]e have the wolf by the ear and feel the danger of either holding or letting him loose. - Jefferson to Lydia Huntley Sigourney, July 18, 18242
"Wolf by the ears" is a phrase attributed to the emperor Tiberius by the biographer Suetonius: "The cause of his hesitation was fear of the dangers which threatened him on every hand, and often led him to say that he was 'holding a wolf by the ears.'"3 Jefferson owned a 1718 edition of Suetonius's works.4
2. Published in the Magazine of American History, XXI (1891), 481. The draft of this letter, in Jefferson's hand, uses the same phrase as in the letter to Holmes: "wolf by the ear." The recipient's copy of the letter, in the hand of Jefferson's granddaughter Virginia and signed by Jefferson, reads "wolf by the ears," which has been repeated in the published version. Transcription available at Founders Online.