الْعِلْمُ كَالنُّورِ فِي الْهِدَايَةِ.
Knowledge resembles light in guiding.
The subject of comparison is al-ʿilm, its analogue al-nūr, the particle is kāf, and the common feature is guidance. An abstract quality is made intelligible through a sensory image.
An adequate simile analysis identifies the exact shared feature, not merely the compared terms.