Sins of the Past is a rare Sorcery card from Ravnica: City of Guilds (RAV), collector number 106. Current market price: $0.46 (foil $3.14), TCGplayer market prices via Scryfall.
Until end of turn, you may cast target instant or sorcery card from your graveyard without paying its mana cost. If that spell would be put into your graveyard, exile it instead. Exile Sins of the Past.