Make sure your neighborhood is friendly to mongooses
(Hebi no namagoroshi wa hito wo kamu;
“A half-killed snake bites a person”)
If you take action but don’t finish the job, you only invite harm. A snake wounded but not finished off, or left only half-dead, will lash out and bite. Once you’ve started something – especially the defeat of a vicious foe – finish the job lest it come back and haunt you. While the “action” left unfinished may be general, this saying often carries a connotation of something potentially dangerous that is not dealt with thoroughly.
We begin four (and five) characters in, with the verb 殺す (korosu), “to kill,” in prenominal form and acting as a noun. This is compounded with the noun 生 (nama), “raw” or “live,” or in this case “unfinished.” The associative particle の (no) attaches this compound to, and allows it to be modified by, the noun 蛇 (hebi), “snake.” This entire noun phrase is marked as the topic of discussion by the particle は (wa). The comment on this topic begins with the noun 人 (hito), “person,” which is marked by the particle を (wo) as the direct object of the verb 噛む (kamu), which appears in conclusive form.
Writing hebi with katakana (ヘビ) or writing kamu as 咬む is a perfectly acceptable orthographic variation.
The phrase 蛇の生殺し on its own can refer to leaving an opponent to suffer after wounding but not killing them, or by extension, any job left half-finished. Things may also be rearranged to give 生殺しの蛇に噛まれる (namagoroshi no hebi ni kamareru), “to be bitten by a half-killed snake,” i.e. “to be harmed after failing to completely root out something bad.”
(“Toubun no aida wa gisei mo naku tero wo fusegu koto ga dekita ga, hebi no namagoroshi wa hito wo kamu koto ni naranai you ni, inbou ni kwawatta mono wo minna taiho suru made yasumazu ni tsutome tsudzukeru tsumori da.”)
[“For the time being, we’ve managed to avert a terror attack without any victims. But to prevent a half-finished job from coming back to bite us, we intend to continue working until every member of the conspiracy is behind bars.”]