502.24a.

Madness is a keyword that represents two abilities. The first is a static ability that functions while the card with madness is in a player's hand. The second is a triggered ability that functions when the first ability is applied. "Madness [cost]" means "If a player would discard this card, that player discards it, but may remove it from the game instead of putting it into his or her graveyard" and "When this card is removed from the game this way, until that player passes next, the player may play it any time he or she could play an instant by paying [cost] rather than paying its mana cost. When the player passes next, he or she puts this card into his or her graveyard."