Musashi stirrups—
though you hang them in earnest,
and place your trust in me,
not to write is cruel,
to write is vexing too.

Meaning

Though you hang your Musashi stirrups in earnest and place your trust in me, not to write is cruel, and to write is vexing too.

Commentary

Episode Thirteen: "Musashi stirrups"

A man in Musashi wrote to a woman in the capital, saying in his letter, "If I speak of it, it is shameful; if I do not speak, it is painful," and on the outside he wrote "Musashi stirrups."
This poem was written and sent in reply by the woman in the capital.

Musashi stirrups were horse gear produced in Musashi Province, on which one places one’s foot. "Sasuga" also refers to a metal fitting used in such gear.
From ancient times through the early Heian period, it seems that when a man went to a distant province, it was common for him to take another woman there. Reading the man’s circumstances in his letter, the woman used words associated with stirrups and pivot-words to express her feelings just as they were.

Source

Ise Monogatari

Other

Musashi stirrups— though you hang them in earnest, and place your trust in me, not to write is cruel, to write is vexing too.

Musashi stirrups—
though you hang them in earnest,
and place your trust in me,
not to write is cruel,
to write is vexing too.