Babylonian Talmud, Baba Metzia 62a

If two are traveling on a journey [far from civilization] and one has a pitcher of water, if both drink, they will both die, but if only one drinks, then that one can reach civilization. Ben Patura taught: It is better that both should drink and die, rather than that one should witness their companion’s death. Until R. Akiva came and taught: “that your fellow may live with you” - your life takes precedence over the other’s life. [Soncino translation. Edited for gender neutrality]