“I think sir, since you care for the advice of an old man, sir, you will find it a very good practise, always to verify your references, sir!”
Advice given to Dean John William Burgon, (29 November 1847), in response to the question: "Every studious man, in the course of a long and thoughtful life, has had occasion to experience the special value of some one axiom or precept. Would you mind giving me the benefit of such a word of advice?"; quoted in Lives of twelve good men, by John William Burgon, 1888, vol. 1 p. 73.
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Martin Joseph Routh 4
Classical scholar and college head 1755–1854Related quotes

Like the latter, it seems to be tinged with a definite scepticism. It suggests a lack of faith in my vision. The impression I retain after hearing you shoot it at me a couple of times is that you consider me to be talking through the back of my neck, and that only a feudal sense of what is fitting restrains you from substituting for it the words 'Says you!'"
Source: Right Ho, Jeeves (1934)

“Thank you, good sir, I owe you one.”
The Poor Gentleman, Act I, Scene 2, reported in Bartlett's Familiar Quotations, 10th ed. (1919).

Rifleman Hagman and Sergeant Patrick Harper, p. 188
Sharpe (Novel Series), Sharpe's Havoc (2003)

“And you, old sir, we are told you prospered once.”
XXIV. 543 (tr. R. Lattimore); Achilles to Priam.
Iliad (c. 750 BC)

To a British military officer (August 1780), as quoted in Washington and the Generals of the American Revolution (1856), by Rufus Wilmot Griswold, William Gilmore Simms, and Edward Duncan Ingraham. J.B. Lippincott, p. 271. Also quoted in "Death of Baron De Kalb" https://books.google.com/books?id=k2QAAAAAYAAJ&pg=PA234&lpg=PA234&dq=%22I+thank+you+sir+for+your+generous+sympathy,+but+I+die+the+death+I+always+prayed+for:+the+death+of+a+soldier+fighting+for+the+rights+of+man%22&source=bl&ots=-93hJzoCYU&sig=tAag8ObQI-ZjiII56viczov02wM&hl=en&sa=X&ei=VlYVVcuJI4KmNsazgYgL&ved=0CCUQ6AEwAQ#v=onepage&q=%22I%20thank%20you%20sir%20for%20your%20generous%20sympathy%2C%20but%20I%20die%20the%20death%20I%20always%20prayed%20for%3A%20the%20death%20of%20a%20soldier%20fighting%20for%20the%20rights%20of%20man%22&f=false (1849), by Benjamin Franklin Ells, The Western Miscellany, Volume 1, p. 233. These were reportedly his last words.
1780s

“"You had no choice, sir." "There's always a choice."”
Lieutenant Robert Knowles and Captain Richard Sharpe on the destruction of Almieda's magazine, p. 239
Sharpe (Novel Series), Sharpe's Gold (1981)

Sergeant Barret and Major Richard Sharpe, p. 273
Sharpe (Novel Series), Sharpe's Honor (1985)

“Sir, I have found you an argument; but I am not obliged to find you an understanding.”
June 1784, p. 545
Life of Samuel Johnson (1791), Vol IV