Buy it when prevention is cheap, not when cure is costly
(Chi ni ite ran wo wasurezu; “In peace, do not forget strife”)
Even in times of peace and safety, it’s still necessary to plan ahead in case something goes wrong. In times of plenty, prepare for scarcity; in times of peace, be ready to deal with disaster or violence. Even when things are going well, make a point of thinking about ways that they could go poorly, and lay plans accordingly.
We begin with the noun 治 (chi), “peace,” although note that in contemporary Japanese this usage is obscure and often adds the meaning of “governance” to compound terms, e.g. 治安 (chian, “public safety/order”). This is marked as the (temporal) location of the verb 居る (iru), “to sit,” “to be,” in conjunctive form and taking the perfective suffix つ (tsu), also in conjunctive form. The following clause begins with the noun 乱 (ran), “disorder,” “war,” marked by the particle を (wo) as the object of the final verb 忘る (wasuru), “to forget,” which is in imperfective form (as 忘れ, wasure) and takes the negative suffix ず (zu) in conclusive form.
This comes to us from a commentary appended to the I Ching (Japanese 『易経』 = Ekikyou) known as the “ten wings” (十翼 = juuyoku) – specifically the “Great Commentary” (繁辞伝 = Keijiden).
Writing chi with homophone 地 (“earth”) is, of course, an error. However, writing ite in kana as いて is acceptable. As we might expect based on the fame and antiquity of its source, this saying also boasts multiple variants, e.g. by replacing 治 with some grammatical form of 安 (an, also “peace”) and 乱 with 厄 (yaku, “disaster”) or 危 (ki, “danger”), and/or perhaps the final verb with the affirmative form of 思う (omou, “to think [of]”), among others.
(“Tekisetsu na gyouseikan to ittara, hotondo no hito ga souzou suru no wa kinkyuu jitai ni nattara reisei ni rinkiouhen ni taiou dekiru jinbutsu da to omou kedo, boku wa somosomo kinkyuu jitai ga okiru mae ni, chi ni ite ran wo wasurezu de, shikkari to sonaete oku no ga ichiban da to omoimasu.”)
[“If you talk about what makes a good public administrator, I think most people imagine someone who stays calm and adaptable during emergencies. But I believe that what’s best is actually someone who thinks about trouble even when things are calm and prepares thoroughly before an emergency situation actually arises.”]