Sheltering Word
Instant
Target creature you control gains hexproof until end of turn. You gain life equal to that creature's toughness. (A creature with hexproof can't be the target of spells or abilities your opponents control.)
Igor Kieryluk
The List (PLST)
• #AVR-192Rulings
If a creature gains hexproof in response to a spell or ability controlled by an opponent that targets only it, that spell or ability doesn’t resolve for having an illegal target when it tries to resolve.
(wotc • 2012-05-01)
Rulings
If a creature gains hexproof in response to a spell or ability controlled by an opponent that targets only it, that spell or ability doesn’t resolve for having an illegal target when it tries to resolve.
(wotc • 2012-05-01)