(Mono ieba kuchibiru samushi aki no kaze;
“When you say something, then your lips will feel the chill of an autumn wind”)
Being nasty will only make you feel bad later; shooting off your mouth invites disaster. Needlessly talking about other people’s (perceived) shortcomings and boasting about your own (perceived) virtues only invites ill-will and misfortune, so it’s better to be circumspect. “Silence is golden.” From the image of opening your mouth (for malicious gossip, etc.) and feeling an unpleasant chill as the autumn breeze brushes your lips.
We begin with noun 物 (mono), “thing,” compounded with verb 言う (iu), “to say.” The latter is in perfective form, with conditional suffix ば (ba), “when(ever).” This dependent clause is followed by noun 唇 (kuchibiru), “lip(s),” with adjective 寒し (samushi), “cold,” in conclusive form. This is followed by what I parse as a separate comment: a noun phrase comprising 秋 (aki), “autumn,” and 風 (kaze), “wind,” joined by associative particle の (no). One might imagine particles (such as an を between 物 and 言えば) or other additions, but these are elided.
Careful readers will already know why the grammatical structure is a bit unusual for a kotowaza: it’s because this is also poetry. This “saying” is a 5-7-5-syllable hokku from the poetic collection『芭蕉庵小文庫』 (Basho-an kobunko) by, well, famed poet Matsuo Bashō.
That said, it’s acceptable to shorten the saying to a pithier form such as 物言えば唇寒し.
The wisdom of keeping one’s mouth shut is not a new topic.
(“Mama, mama, tesuto de hyakuten manten totta!” “Yoku dekita wa ne! Ureshii ne.” “Demo, Haru-chan wa” “Sonna no iwanakute ii wa yo, mono ieba kuchibiru samushi.” “E? Futsuu ni attakai kedo.”)
[“Mama, mama, I got a perfect hundred on the test!”
“Well done! I’m so happy!”
“But Haru got a—”
“No need for that. Say too much and it chills the mouth.”
“Uh? But I’m as warm as usual.”]