兄弟阋于墙，外御其侮
xiōng​dì​xì​yú​qiáng​wài​yù​qí​wǔ

internal disunity dissolves at the threat of invasion

兄弟阋于墙，外御其侮 兄弟鬩於墻，外禦其侮 xiōng​dì​xì​yú​qiáng​wài​yù​qí​wǔ
internal disunity dissolves at the threat of invasion
internal disunity dissolves at the threat of an invasion from outside; siblings may fight at home but will join forces against outsiders