Mystical Teachings is a common Instant card from Modern Masters 2017 (MM3), collector number 44. Current market price: $0.31 (foil $0.39), TCGplayer market prices via Scryfall.
Search your library for an instant card or a card with flash, reveal it, put it into your hand, then shuffle. Flashback {5}{B} (You may cast this card from your graveyard for its flashback cost. Then exile it.)