First do no harm

Make a habit of two things: to help; or at least to do no harm.

The physician must be able to tell the antecedents, know the present, and foretell the future — must mediate these things, and have two special objects in view with regard to disease, namely, to do good or to do no harm.

Whenever a doctor cannot do good, he must be kept from doing harm.

The Hippocratic Oath says do no harm. It's the Hypocritical Oath that says do no harm to one's political future.

“Ars longa, vita brevis." (Life is short, the art long.)