“When the Union needs my poor support, in peace or in war, I induge the hope that I shall not fail in the performance of any duty which may be required me. At any rate, I hope not to fall behind that class of men who are, on all occasions, blurting their devotion to the Union into the unwilling ears of the country.”

Preface, In the Net of Stars, 1909
Other Quotes

1960s, October surprise speech (1968)
Context: What we won when all of our people united just must not now be lost in suspicion, distrust, selfishness, and politics among any of our people. Believing this as I do, I have concluded that I should not permit the Presidency to become involved in the partisan divisions that are developing in this political year. With America's sons in the fields far away, with America's future under challenge right here at home, with our hopes and the world's hopes for peace in the balance every day, I do not believe that I should devote an hour or a day of my time to any personal partisan causes or to any duties other than the awesome duties of this office — the Presidency of your country. Accordingly, I shall not seek, and I will not accept, the nomination of my party for another term as your President.

Speech in the Senate, February 14, 1850, in response to a speech by Senator Henry S. Foote of Mississippi, who had "lectured" Clay on the allegiance which he owed to the South as a senator from a Southern state. From The Life, Correspondence, and Speeches of Henry Clay (Vol. 3); ed. Calvin Colton: A. S. Barnes & Co., 1857.

Broadcast (27 September 1938), quoted in The Times (28 September 1938), p. 10
Prime Minister

Joseph Lane (May 7, 1850) " Governor Joseph Lane Legislative Message, 1850 http://records.sos.state.or.us/ORSOSWebDrawer/Recordpdf/6777826", Oregon State Archives, Oregon Secretary of State, Oregon Provisional and Territorial Records, 1850, Calendar No. 10571.

1870s, Seventh State of the Union Address (1875)
Context: I am happy to announce the passage of an act by the General Cortes of Portugal, proclaimed since the adjournment of Congress, for the abolition of servitude in the Portuguese colonies. It is to be hoped that such legislation may be another step toward the great consummation to be reached, when no man shall be permitted, directly or indirectly, under any guise, excuse, or form of law, to hold his fellow-man in bondage. I am of opinion also that it is the duty of the United States, as contributing toward that end, and required by the spirit of the age in which we live, to provide by suitable legislation that no citizen of the United States shall hold slaves as property in any other country or be interested therein.

Speech to Congress (8 January 1861).
Context: It is said that serious apprehensions are to some extent entertained (in which I do not share) that the peace of this District may be disturbed before the 4th of March next. In any event, it will be my duty to preserve it, and this duty shall be performed.
In conclusion it may be permitted to me to remark that I have often warned my countrymen of the dangers which now surround us. This may be the last time I shall refer to the subject officially. I feel that my duty has been faithfully, though it may be imperfectly, performed, and, whatever the result may be, I shall carry to my grave the consciousness that I at least meant well for my country.

Source: "Pledge during an oath-taking ceremony at the ordination hall of the Temple of the Emerald Buddha after his investiture as Crown Prince" https://www.bangkokpost.com/specials/royal-coronation/royal_speeches.php (28 July 1972)