“Well, den, dis is de way it look to me, Huck. Ef it wuz HIM dat ‘uz bein’ sot free, en one er de boys wuz to git shot, would he say, ‘Go on en save me, nemmine ’bout a doctor f’r to save dis one?’ Is dat like Mars Tom Sawyer? Would he say dat? You BET he wouldn’t! WELL, den, is JIM gywne to say it? No, sah – I doan’ budge a step out’n dis place ‘dout a DOCTOR, not if it’s forty year!”
– Mark Twain
The Adventures of Huckleberry Finn, Chapter 40. When Tom Sawyer takes a bullet for him, runaway slave Jim says they should get a doctor for Tom, since he says Tom would if the situation was reversed. Jim believes Tom would sacrifice his own freedom to save Jim.