adverb
Archaic adverb meaning 'clearly' or 'brightly'. Not used in modern Japanese; found only in classical texts.
古典では「月がさやに照る」のように使われた。
In classical literature, it was used as in 'the moon shines brightly'.
adverb
Archaic adverb meaning 'cleanly' or 'purely'. Also restricted to classical usage.
「さやに清き心」といった古い表現がある。
There is an old expression like 'a purely clean heart'.