兄弟鬩於墻，外禦其侮

internal disunity dissolves at the threat of an invasion from outside (idiom)

brothers / younger brother / CL:個|个[ge4] / I, me (humble term used by men in public speech) / brotherly / fraternal

elder brother

younger brother / junior male / I (modest word in letter)

variant of 悌[ti4]

to argue / to quarrel

surname Yu / Taiwan pr. [Yu2]

(literary) Oh! / Ah!

(of time or place) in; at; on / (indicating any indirect relation) to; toward; vis-à-vis; with regard to; for / (indicating a source) from; out of / (used in comparison) than / (used in the passive voice) by

variant of 牆|墙[qiang2], wall

outside / in addition / foreign / external

to defend / to resist

his / her / its / their / that / such / it (refers to sth preceding it)

to insult / to ridicule / to disgrace