“You promise." "I swear on the angel. The hell with that. I swear on us." "Why us?" "Because there isn't anything I believe in more.”

Source: City of Fallen Angels

The atheist drew up his head. "And I," he said, "give my word."
The Ball and the Cross (1909), part II: "The Religion of the Stipendiary Magistrate", last paragraphs

1970s, Remarks on pardoning Nixon (1974)
Context: My conscience tells me it is my duty, not merely to proclaim domestic tranquillity but to use every means that I have to insure it.
I do believe that the buck stops here, that I cannot rely upon public opinion polls to tell me what is right.
I do believe that right makes might and that if I am wrong, 10 angels swearing I was right would make no difference.
I do believe, with all my heart and mind and spirit, that I, not as President but as a humble servant of God, will receive justice without mercy if I fail to show mercy.
Finally, I feel that Richard Nixon and his loved ones have suffered enough and will continue to suffer, no matter what I do, no matter what we, as a great and good nation, can do together to make his goal of peace come true.

Mum Wants A Bungalow Tour [2003]

Source: The Red Pyramid

As quoted in The Life and Public Service of Abraham Lincoln (1865) by Henry J. Raymond
Posthumous attributions
Context: If I were to try to read, much less answer, all the attacks made on me, this shop might as well be closed for any other business. I do the very best I know how — the very best I can; and I mean to keep doing so until the end. If the end brings me out all right, what's said against me won't amount to anything. If the end brings me out wrong, ten angels swearing I was right would make no difference.

Source: Lady Holland's Memoir (1855), p. 257: Let us swear an eternal friendship. Poetry of the Anti-Jacobin. The Rovers

Act IV, sc. i
Le Bourgeois Gentilhomme (1670)