Notes from Wikiquote
As quoted in Short Sayings of Great Men: With Historical and Explanatory Notes (1882) by Samuel Arthur Bent, p. 455
Variants
Poke not the fire with a sword.
More quotes by Pythagoras
Let no one persuade you by word or deed to do or say whatever is not best for you.
Rest satisfied with doing well, and leave others to talk of you as they please.
Number is the ruler of forms and ideas, and the cause of gods and daemons.
Assist a man in raising a burden; but do not assist him in laying it down.
Attribution
Quote text and notes from Wikiquote: Pythagoras (page history), available under CC BY-SA 4.0. Source quality and labels are our own summary of what Wikiquote records.