This card makes you immune to damage that would take you below 1 life point. [Arab FAQ 1994/01/05]
Does not prevent effects which reduce your life without doing damage. [Arab FAQ 1994/01/05]
The replacement happens automatically at the time damage would be dealt. [D'Angelo 2000/02/25]
The ability works up until Ali enters the graveyard, so if he takes lethal damage or is destroyed at the same time you take damage, the ability does help you. If the damage occurs after it goes to the graveyard (such as with Creature Bond), however, it is not affected by the Ali which is no longer in play. [D'Angelo 2000/02/25]
Does not prevent damage, it prevents the damage from turning into loss of life. So the full damage is dealt, but the full loss of life is not applied. [D'Angelo 2000/02/25]
Does not affect damage if you are already at zero or negative life. You still take it all. [WotC Rules Team 1996/06/27]
Vintage tournaments (see Rule 801) restricted this card from 1994/01/25 to 1996/04/01.
Extended tournaments (see Rule 803) have always banned this card.
Note - This card was creature type "Ali-from-Cairo" until Oracle 2007/10/01, when it became "Human".
Arabian Nights
(Uncommon)