Question: Since lightsabers give off a visible glow, I could see a Jedi or a Sith using their lightsaber as a lighting source. They were already used as tools (at least in Episode I) so there are some non-violent uses to a lightsaber. Has any Jedi or Sith used their lightsaber in this manner in canon works?

Answer: 
Savage Opress used his lightsaber as a light source in the season 4 *The Clone Wars* episode "Brothers" (episode 21).

![Savage Opress uses lightsaber as light source in S04E21](https://i.stack.imgur.com/91inF.jpg)
When Luke is being tested by Yoda at the tree of the Dark Side, he lights his saber as he enters the tunnel. I always assumed it was in order to see by its light.

This is supported by the official novelization as mentioned by [Valorum](https://scifi.stackexchange.com/users/20774/valorum).

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> He held his glowing sword in front of him and noticed an object on the cave floor. Pointing his lightsaber downward, Luke illuminated a black, shiny beetle the size of his hand. In an instant, the thing scurried up the slimy wall to join a cluster of its mates.
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