Oshieokite irinishi tsuki no nakariseba ikade omoi o nishi ni kakemashi - Kinyo Wakashu(English Translation & Meaning)

教へおきて入りにし月のなかりせば
いかで思ひを西にかけまし

Roma-ji: Oshieokite irinishi tsuki no nakariseba ikade omoi o nishi ni kakemashi
English Translation: Had there been no moon
that left its teachings to us
and sank in the west,
how could I have set my heart
upon that western realm
Meaning: Had there been no moon that left its teachings behind and sank below the hills, how could I ever have turned my heart toward the west?
Commentary: Book Ten Miscellaneous Poems II 631

Had there been no moon that left its teachings behind and sank into the western hills, how could the poet have set her heart on the west? Likening the setting moon to the Buddha, who left his teachings and passed into nirvana, she expresses gratitude that only through that guidance can she aspire to the Western Pure Land.
Following the moon flowing west in the preceding poem, 630, this poem also sings of the moon sinking in the west. Poems taking the moon as a guide on the Buddhist path continue from 628 in this book.
The author, Higo of the Kyōgoku Regent's Household, was the daughter of Fujiwara no Sadanari, Governor of Higo, and served as a lady-in-waiting in the household of the Kyōgoku Regent Fujiwara no Morozane.

First line, 'oshieokite', means having left the teachings, pointing to the teachings the Buddha left behind.
Second line, 'irinishi tsuki no', means the moon that has set, the perfective nu with the attributive of the past ki. The setting of the moon is overlaid with the Buddha's passing into nirvana.
Third line, 'nakariseba', means had there been none, se, the irrealis of the past ki, with ba, answering mashi in the final line to form a counterfactual.
Fourth line, 'ikade omoi o', means how could my heart, the adverb ikade carrying a rhetorical sense.
Final line, 'nishi ni kakemashi', means could I have set it on the west, closing with the counterfactual mashi. The west means the Western Pure Land, taking up nishi e in the preceding poem, 630.
Author: Kyōgoku Kanpaku-ke no Higo
Source: Kinyo Wakashu
Prev Poem: Amidabu to tonauru koe ni yume samete nishi e nagaruru tsuki o koso mire
Next Poem: Kaku bakari kochi chō kaze no fuku o mite chiri no utagai o okosazu mogana