كإزالة الحجاب في تشبيه الحجة بالشمس
As with removing a veil when comparing an argument to the sun.
Sunlight can reveal what was obscured by darkness; a strong proof or argument may likewise remove a mental obscurity or doubt. The shared relation is bringing clarity by dispelling concealment.
“Removing a veil” is not an essential part of the sun’s nature, nor does a proof literally lift a cloth. The resemblance concerns a relational effect: something is hidden, an obstacle is removed, and clarity becomes possible. That relation, rather than a literal material action, gives the simile force.