classic waka stream

Because it is shallow
Only sleeves are wet, perhaps,
In this river of tears;
If I heard your very self
Flowing there, I would trust it.

Meaning
Because your feeling is shallow, it must be only your sleeves that grow wet in this river of tears. If I were to hear that even your whole self was carried away by those tears, then I might rely upon your love.
Commentary
107. River of Tears

There was a man of high rank. Fujiwara no Toshiyuki, who held the office of Naiki (responsible for drafting imperial edicts and keeping official records), had taken a liking to a woman who served in that man’s household and sought a relationship with her.
However, the woman was young and inexperienced. She was uncertain even in writing letters, unable to speak in refined language, and she did not compose poems. Therefore the man prepared draft poems for her, had her copy them, and sent them to Toshiyuki.
The poem was composed by the man as a reply on the woman’s behalf to Toshiyuki’s poem: “In lonely contemplation, tears surpass the flowing river—my sleeves are drenched, yet there is no way to meet you.”
When Toshiyuki heard the poem, he was deeply moved and is said to have placed the letter carefully in a document box and treasured it.

The man refers to Ariwara no Narihira, and this exchange of poems is also included in the Kokinshū. Because Narihira was well known for his many love affairs, he understood a man’s heart and could compose a poem that would draw out Toshiyuki’s feelings on the woman’s behalf. In this poem he subtly tests Toshiyuki’s sincerity, suggesting that perhaps he has shed only enough tears to wet his sleeves.
Source
Ise Monogatari
Other