Per Ignem incedis.

Or, as Horace gives it,

–––«Incedis per ignes
Suppositos cineri doloso».

You are treading on hot ashes. You are engaged in a difficult and hazardous business. Take care, we say, you do not burn yourself, or, burn your fingers. Johnson uses the phrase, when entering on the lives of the poets, who lived near his time, or were his contemporaries; meaning, that by speaking freely of them, and giving his sentiments of their works there was danger of offending their friends or relatives. The adage may also mean, as you are treading on hot ashes, that is, are in jeopardy, get out of the business, conciliate the parties whom you have offended, as soon as you can, as you would run or hasten over a floor that is burning; the flame which is at present smothered, may burst out and destroy you. That this is also intimated, seems probable from the following.

Non incedis per Ignem.

You are not walking over a furnace, which was used to be said to persons appearing to be in great haste, but who had no urgent business.