Where does “освящать” come from?

освящать (Russian) comes from Russian освяти́ть, from Russian свято́й, from Old East Slavic свѧтъ, from Proto-Slavic svętъ, from Proto-Balto-Slavic śwentas, from Proto-Indo-European ḱwen- — holy, sacred.

освящать (Russian): to sanctify, to hallow, to consecrate