Archaic expression; modern Japanese normally uses 針の穴 (はりのあな) for the eye of a needle. This phrase may appear in older texts or fixed sayings.
See also: 針の穴 (はりのあな)
In old documents, it is sometimes written as 針の耳.
The phrase literally means 'ear of a needle', using 耳 (ear) metaphorically for the eye. The exact origin is uncertain, but it follows a common cross-linguistic metaphor.