classic waka stream

あまの川空なるものと聞きしかど
わが目のまへのなみだなりけり
Roma-ji

Ama no kawa sora naru mono to kikishikado waga me no mae no namida narikeri

English Translation
The River of Heaven
I had always heard, was a
thing up in the sky
and it turns out to be the
tears here in front of my eyes
Meaning
The River of Heaven, I had always heard, was a thing up in the sky. And it turns out to be the tears here before my eyes.
Commentary
103 The River of Heaven

At the height of his career as a lover, Heichū went to the market, for in those days people of rank went to the market to look for lovers. Women in the empress's service were there, and he pressed his suit ardently. When he wrote to them, they had someone ask which of the several women in the carriage his letter was meant for, and he answered with "Momoshiki no tamoto no kazu wa mishikadomo wakite omoi no iro zo koishiki". She was the daughter of the Governor of Musashi, and had been wearing a robe of deep scarlet silk. She answered, and they became lovers. But after their one night together no word came from him, that morning or that evening; five and six days passed, and she wept and would not eat, and at last cut off her long hair with her own hands and became a nun. On his side, his superior had carried him off the very next morning, then came attendance on the retired emperor at the Ōi river, and then a closed direction that obliged him to lodge elsewhere. He was on the point of writing at last when a servant of her house arrived with a letter wrapping a lock of cut hair, on which was written "Ama no kawa sora naru mono to kikishikado waga me no mae no namida narikeri". Everything went dark before him; he answered with "Yo o waburu namida nagarete hayaku tomo ama no kawa ni wa sa ya wa narubeki" and went to her himself. She had shut herself in the storeroom, and though he begged to hear her voice she did not answer. He made of this, we are told, the most extraordinary thing in the world. That is the whole of the section.
Heichū is Taira no Sadafun, known as a great lover, who also appears in the forty-sixth and sixty-fourth sections. The woman was a daughter of the Governor of Musashi and served the empress. The storeroom was a windowless inner room with a door and a light-opening.
The setting is after she had taken the veil. Five and six days passed with no word from Heichū; she wept and would not eat, and at last cut off her hair and became a nun herself.
What prompted the poem was that act. It reached him with the cut hair wrapped inside the letter.
Reading it, everything went dark before him; he answered and went to her himself.

The first word of the river's name is also the word for a nun, so that the River of Heaven and her taking the veil stand in one word.
The pun opens only when the letter is opened: on the page alone it is a poem about the sky, and with the lock of hair beside it, it is the news of her renunciation.
The third line grants what she had heard about the river being up in the sky, and turns on it.
The closing marks the discovery: it was the tears in front of her. What should be far off in the heavens turns out to be her own weeping. It announces her renunciation without a single word of reproach.
Source
Yamato Monogatari
Other