綸言汗の如し
(Ringen ase no gotoshi; “Imperial words are like sweat.”)

Definition:

Words, like sweat, cannot be put back where they came from. Once a ruler has issued a command or decree, it cannot be changed or undone. Implicit in this saying is the warning for people in government (or in positions of influence and power in general) to watch their words and conduct; a careless word or poorly-phrased ruling or law can have wide-ranging consequences, even though we now live in an age when leaders are free to rescind, rephrase, and repent their words, and amend the laws they’ve passed.

Breakdown:

綸言 (ringen) is a noun meaning “imperial words,” specifically official orders and pronouncements. Since this is old-fashioned Japanese, this noun is not accompanied by anything special, but modern Japanese would likely add the topic marker here. Next we have another noun, 汗 (ase), “sweat.” It’s connected by the associative particle の (no) to adjectivally-conjugating auxiliary verb 如し (gotoshi), “[be] like,” in sentence-final form.

Notes:

Some people may replace the first character with 倫 (also pronounced rin, but meaning “ethics” or “morality,”) but this is an error.

This is the ri entry in both the Kyoto and Osaka Iroha karuta sets. It’s based on a longer (more explicit) passage from the Book of Han.

Example sentence:
(Again borrowed from a dictionary)

「日本の政治家は、綸言汗の如しという言葉を知らないのか」

(“Nihon no seijika wa, ringen ase no gotoshi to iu kotoba wo shiranai no ka.”)

[“Don’t politicians in Japan know it’s said that words, like sweat, can’t be taken back?”]