Plagiarize

If you target a player whose library is empty, any effect or turn-based action that would cause that player to draw a card will cause you to draw a card instead. It doesn’t matter that the other player would be unable to draw.

You draw the card from your library as normal, not from your opponent’s library.

If you and your opponent each cast Plagiarize on each other during the same turn, the two spells effectively cancel each other out. You will draw cards when you normally would and so will your opponent.