All things must pass:
This is the rule of life and death.
End life, end death:
Enter Nirvana, become joyful.

I've covered a lot of compounds that come from classical Chinese literature. Here's one from the Japanese canon, specifically the Tale of the Heike (平家物語).

一味同心
ichi mi dou shin
one interest, same spirit

Here it is in context, which means section 8.3 of ol' Heikalot, at least according to this rather excellent online version. I've bolded いちみどうしん (the hiragana for 一味同心) and its English equivalent in my translation.

ぶんごのくには、刑部卿ざんみよりすけのきやうのくになりけり。しそくよりつねのあそんをだいくわんにおかれたりけるが、きやうよりよりつねのもとへししやをたてて、へいけはすでにしんめいにもはなたれたてまつり、きみにもすてられまゐらせて、ていとをいでて、なみのうへにただよふおちうととなれり。しかるをきうしうにたうのものどもがうけとつて、もてあつかふらんことこそしかるべからね。たうごくにおいては、いつかうしたがふべからず。とうほくこくといちみどうしんして、くこくのうちをおひいだしたてまつるべきよし、のたまひつかはされたりければ、これををがたのさぶらうこれよしにげぢす。

The province of Bungo was ruled by Yorisuke, Secretary of Justice, Third Rank. His son, the courtier Yoritsune, had been put in charge, but the capital sent a messenger to Yoritsune. "The Heike have already become separated from the gods, been abandoned by the Emperor, left the Imperial Capital and become defeated soldiers, bobbing on the waves. Therefore, it is not acceptable for the people of the Nine Provinces and Two Islands* to take them in. Associate with them not, but rather join together with the East and the North [of Japan] and drive them out entirely," were the orders, and so he delegated the task to Ogata no Saburou Koreyoshi.

* i.e. Kyushu + Ikijima and Tsushimatou

Well, you probably guessed that it meant something like that already, huh?

The opening sentence Tale of the Heike includes another of my favourite four-character compounds -- hell, one of my favourite phrases, period. This one is much more famous and comes from the Nirvana Sutra (涅槃經).

諸行無常
sho gyou mu jou
everything goes, nothing eternal

The full context is:

祗園精舎の鐘の声、諸行無常の響きあり

The voice of the bells of Gion Shouja,
An echo of "All Things Must Pass"

(Gion in this case having nothing to do with Kyoto's geisha district, but referring instead to Jetavana Vihara in Savatthi.)