Rule 444.2.a
If the instruction to Pay resources is part of paying costs for a card or ability, choosing not to pay those resources will cause the act of playing the card or ability to be undone. See rule 358. Check Legality for more information.
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If the instruction to Pay resources is part of paying costs for a card or ability, choosing not to pay those resources will cause the act of playing the card or ability to be undone. See rule 358. Check Legality for more information.