思ひに分ぬ Omoi ni wakanu
越の山 Koshi no yama
ふる白雪も Furu shirayuki mo
鳴るいかづちも Naru ikazuchi mo.
Whether summer or winter,
the mountain of Koshi
is free from discriminative thinking.
It sees equally
falling of white snowflakes,
or roaring of thunder.
The mountain of Koshi (越の山) may refer to the sacred mountain Mt. Hakusan (白山, white mountain). Koshi (越, another pronunciation is Etsu) was the name of the large area in Hokuriku Region which included Echizen (越前, presently Fukui Prefecture), Kaga (加賀, Ishikawa Prefecture), Ecchu (越中, Toyama Prefecture), and Echigo (越後, Niigata Prefecture). In ancient times, this mountain was called Koshi no Shirane (越白嶺, the white peak of Koshi).
In the Shugendo tradition (a Japanese mountain asceticism-shamanism incorporating Shinto and Buddhist concepts), Hakusan has been considered a sacred mountain since the Nara period (8th century CE). Not far from Eiheiji, there is a trail to climb Hakusan; it is one of three starting points beginning at a temple named Heisenji.
There is a story in Dōgen's biography, Kenzeiki, regarding the god enshrined on Hakusan named Hakusan Myori Daigongen (白山妙理大権現). The day before Dōgen went back to Japan from China, he tried to copy Hekiganroku (Blue Cliff Record). Since it was a large text, he did not have enough time. That night, the god of Hakusan appeared and helped Dōgen copy the text. Later in Soto Zen tradition, the god of Hakusan was considered as the guardian god of Eiheiji.
The great sacred mountain Hakusan does not discriminate between summer and winter. The mountain is immovable, accepting all of the different conditions and things happening in the four seasons, including roaring thunder in the summer and white snow in the winter.
This waka reminds me of what Dōgen wrote in the Tenzokyokun (The Instructions for the Tenzo) regarding magnanimous mind:
"As for what is called magnanimous mind, this mind is like the great mountains or like the great ocean; it is not biased or contentious mind. Carrying half a pound, do not take it lightly; lifting forty pounds should not seem heavy. Although drawn by the voices of spring, do not allow your heart to fall. The four seasons cooperate in a single scene; regard light and heavy with a single eye. On this single occasion you must write the word 'great.' You must know the word 'great.' You must learn the word 'great.'"