godan verb (-su)
Used when the subject (often a superior or someone in a position to inform) tells or makes something known to someone. Not inherently honorific; the honorific use is covered in sense 2.
変更があれば、事前に知らせてください。
If there are any changes, please let me know in advance.
godan verb (-su)
Honorific (sonkeigo) equivalent of 知る. Used to show respect toward the person who knows something. Often used in the form ご存知 (ごぞんじ) in modern Japanese, but 知らす can appear in formal or literary contexts.
陛下はその件を知らす。
His Majesty knows about that matter.
godan verb (-su)
Honorific (sonkeigo) equivalent of 治める or 統治する, used for a sovereign or high authority. Rare and mostly found in historical or formal contexts.
天皇が国を知らす。
The Emperor reigns over the country. (honorific)