Sorcerer's Library

Sorcerer's Library enters the battlefield tapped.
{t}: Add {u} or {r}
{1}{u}{r}{t}: Target spell gains Rebound (If this spell
was cast from your hand, instead of putting it into your graveyard as it resolves, exile it and, at the beginning of
your next upkeep, you may cast this card from exile without paying its mana cost.).