Historical Rules · 22 April 2021
Rule 702.52a
Official source text from the 22 April 2021 Rules release
Dredge is a static ability that functions only while the card with dredge is in a player’s graveyard. “Dredge N” means “As long as you have at least N cards in your library, if you would draw a card, you may instead mill N cards and return this card from your graveyard to your hand.”