Prevent the next 3 damage that would be dealt to any target this turn by a source of your choice. You gain 3 life.
4/27/2018 Healing Grace only targets the creature, planeswalker, or player that will receive the damage prevention “shield.” The source isn’t targeted.
4/27/2018 You choose only one source, even if that source won’t deal 3 damage.
4/27/2018 You gain 3 life as Healing Grace resolves, even if there’s no damage to prevent.