“Whenever a great doctor treats an illness, he must first of all calm his spirit and fix his resolve. He should not give way to wishes and desires but should develop first of all an attitude of compassion. He must vow to rescue the sufferings of all sentient beings. If someone comes for help, he must not ask if the patient is noble or common, rich or poor, old or young, beautiful or ugly. Enemies, relatives, good friends, Chinese or barbarians, foolish and wise, all are the same. He should think of them as his closest relatives. He should not be overly circumspect and worry about omens or his own life. He should look on others’ sufferings as his own and be deeply concerned. He should not hide away in the mountains. Day and night, in cold and heat, in hunger, thirst, and fatigue, he should single-mindedly go to the rescue. Whoever acts in this manner is a great doctor for the living. Whoever acts contrary is a great thief for those who still have their spirits.” - Sun Simiao, "On the Absolute Sincerity of Great Physicians,"
Numerous sources of information on Sun Simiao exist but here is one suggestion for further reading