Tournament rule 702.14.a.1

If a player recycled and replaced more than 2 cards during their mulligan, the next opponent in turn order of the erroring player looks at that player’s hand and may choose cards up to the number of extra cards mulliganed to have that player recycle and replace.

• 702.14.a.1.a Example: If a player accidentally mulliganed 3 cards, the next opponent in turn order would look at that player's hand…

Official Tournament Rules