Selfless Cathar

Oracle Text

1W, Sacrifice Selfless Cathar: Creatures you control get +1/+1 until end of turn.

Card Rulings

9/22/2011 You can activate Selfless Cathar’s ability even if you control no other creatures.
9/22/2011 Only creatures you control when Selfless Cathar’s ability resolves will be affected. Creatures that enter the battlefield or that you gain control of later in the turn will not.