classic waka stream

If the sleeve of one
whose fragrance is his by birth
should brush against it
the flower too will scatter
a name beyond all telling

Meaning
If the sleeve of one whose fragrance is his from birth should brush the flower, the flower too will scatter a name beyond all telling.
Commentary
Part Three: Kobai

 The boy brought the previous day's answer back and showed it to the Dainagon, who said it was a galling way to put it. Hearing that they would not countenance how far he had gone toward a life of gallantry, he said, the Prince puts on a great show of gravity in front of the Minister of the Right and ourselves, which is amusing; a man with everything it takes to be a rake, forcing himself to look sober, is not much to look at either. Still he did not give up, and when he sent the boy to the palace again that day he sent this poem with him, adding below it, in a serious tone, that he was aware how gallant his own words sounded and begged pardon for them. Niou took it that the Dainagon meant, by an exchange of letters, to give the world the impression that the match was going forward; and yet in spite of himself he was moved.

 "The fragrance that is his by birth" is the scent Niou has had from birth, taken up from the chapter where it is set beside Kaoru's. "If the sleeve of one whose fragrance is his should brush against it" means: if he should come to her as a husband. The flower is Naka no Kimi, and to scatter a name beyond all telling is to have her renown spread through the world. The scattering of a flower's scent on the wind and the spreading of a reputation are laid one over the other in the single word "scatter." Though he has just been refused, he praises the other man's own fragrance and presses on with an argument framed as being to the Prince's advantage: the poem shows exactly how set the Dainagon is on the match.
Author
Murasaki Shikibu
Source
Genji Monogatari
Other