Each card that’s revealed to pay the cost remains revealed until the ability leaves the stack.
, Reveal X green cards from your hand, Sacrifice this creature: Target creature gets +X/+X until end of turn.
A card that’s already revealed for another cost or because of an effect can be revealed to pay this cost.
If one of the cards that’s revealed to pay the cost leaves its owner’s hand before the ability resolves, it stops being revealed, but the value of X is not affected.
, Reveal X green cards from your hand,