When Scholar of Combustion enters, exile up to one target instant or sorcery card from your graveyard. You may cast that card until the end of your next turn. (You still pay its costs. Timing rules still apply.)
"If the fire is silent, I'm technically not breaking the library rules!"
You pay all costs and follow all timing rules for the instant or sorcery card cast with the permission granted by Scholar of Combustion's ability. For example, if the exiled card is a sorcery, you may cast it only during your main phase while the stack is empty.
Random a card of Magic: The Gathering (MTG), but you can also roll the D20 dice, random a Planeswalker, have fun with the random rules and more.