An injunction to do no harm is part of the Hippocratic oath, and the actual text has multiple translations, so I don’t think it’s too far-fetched to attribute “first, do no harm” to the oath.
The phrase “first, do no harm” is often, incorrectly, attributed to the oath.
On the other hand:
The origin of the phrase is uncertain. The Hippocratic Oath includes the promise “to abstain from doing harm” but not the precise phrase. Perhaps the closest approximation in the Hippocratic Corpus is in Epidemics: “The physician must...have two special objects in view with regard to disease, namely, to do good or to do no harm”.
An injunction to do no harm is part of the Hippocratic oath, and the actual text has multiple translations, so I don’t think it’s too far-fetched to attribute “first, do no harm” to the oath.
Obligatory wikipedia link.
On the other hand:
This was from the article on first, do no harm.