Text (US+errata): Exile ~this~. Each player discards his or her hand, then returns up to three cards from his or her graveyard to his or her hand. [Oracle 2009/07/08]
You can get fewer than 3 cards if you want. [DeLaney 1998/10/05]
You can pick up any of the cards you discarded since you do not choose the cards until after you discard. [WotC Rules Team 1998/10/18]
