Yorozuyo wa makasetarubeshi iwashimizu nagaki nagare o kimi ni yosoete - Kinyo Wakashu(English Translation & Meaning)

万代はまかせたるべし石清水
長き流れを君によそへて

Roma-ji: Yorozuyo wa makasetarubeshi iwashimizu nagaki nagare o kimi ni yosoete
English Translation: For ten thousand ages
we may leave it all to you,
spring of Iwashimizu,
likening your long, long stream
to the reign of our lord
Meaning: The ten thousand ages may be left to the spring of Iwashimizu, likening its long, unbroken stream to the reign of our lord.
Commentary: Book Five Celebration Poems 306

Likening the long, unbroken stream of Iwashimizu to the sovereign's reign, the poem says the ten thousand ages may simply be left to the spring. With makasu meaning both to entrust and to draw water, it celebrates the reign through the spring on Otokoyama where the Iwashimizu Hachiman Shrine stands.
Taking up 'the ages flowing on' in the preceding poem, 305, this poem too likens a 'long stream' to the reign.
From poem 305 through poem 310 in this book come poems celebrating a thousand and ten thousand ages through such things as bamboo, the spring of Iwashimizu, pines, cherry blossoms and the poet's own self.

First line, 'yorozuyo wa', means ten thousand ages, showing the length of the reign.
Second line, 'makasetarubeshi', is a pivot word in which makase means both to entrust and to draw water into a field, left in kana. The poem breaks after the second line and the lower half is inverted.
Third line, 'iwashimizu', is the spring on Otokoyama in Yamashiro, a poetic place known as the seat of the Iwashimizu Hachiman Shrine.
Fourth line, 'nagaki nagare o', means its long, unbroken stream, likening a stream to the reign as 'the ages flowing on' does in the preceding poem, 305.
Final line, 'kimi ni yosoete', means likening it to the reign of our lord.
Source: Kinyo Wakashu
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