寄らば from 寄らば大樹の陰


I have trouble understanding the 寄らば from:

> 寄{よ}らば大樹{たいじゅ}の陰{かげ}.

I know it comes from 寄る (to approach/to come near). But how does it becomes
寄らば and what meaning it implies?

The ば should be the same as 寄れば. But I have no idea about the ら...




寄らば is the _classical_ (文語) or _archaic_ (古語) conditional-form of 寄る. In
modern standard Japanese, it's 寄れば.

In modern Japanese, the conditional-form (aka ba-form) of a verb ends with
"-eba", as you already know. In archaic Japanese, however, some verbs (namely
四段動詞) took this "-aba" form. (And "-eba" was used for different purposes
similar to "because" or "even though".) Actually this "-a + ba" is the [未然形
("irrealis form") of a
verb](https://en.wikipedia.org/wiki/Classical_Japanese_language#Conjugation_table)
followed by the conjunctive particle ば. But it's not worth memorizing this
table unless you're studying classic Japanese literature.

You can see this archaic form today in proverbs like this one and fixed
phrases such as
[隙あらば](http://ejje.weblio.jp/sentence/content/%E9%9A%99%E3%81%82%E3%82%89%E3%81%B0%E3%81%A8)
(隙があれば, "if there is any chance") and
[死なばもろとも](http://jisho.org/search/%E6%AD%BB%E3%81%AA%E3%81%B0%E3%82%82%E3%82%8D%E3%81%A8%E3%82%82).




寄らば is the _classical_ (文語) or _archaic_ (古語) conditional-form of 寄る. In
modern standard Japanese, it's 寄れば.

In modern Japanese, the conditional-form (aka ba-form) of a verb ends with
"-eba", as you already know. In archaic Japanese, however, some verbs (namely
四段動詞) took this "-aba" form. (And "-eba" was used for different purposes
similar to "because" or "even though".) Actually this "-a + ba" is the [未然形
("irrealis form") of a
verb](https://en.wikipedia.org/wiki/Classical_Japanese_language#Conjugation_table)
followed by the conjunctive particle ば. But it's not worth memorizing this
table unless you're studying classic Japanese literature.

You can see this archaic form today in proverbs like this one and fixed
phrases such as
[隙あらば](http://ejje.weblio.jp/sentence/content/%E9%9A%99%E3%81%82%E3%82%89%E3%81%B0%E3%81%A8)
(隙があれば, "if there is any chance") and
[死なばもろとも](http://jisho.org/search/%E6%AD%BB%E3%81%AA%E3%81%B0%E3%82%82%E3%82%8D%E3%81%A8%E3%82%82).

