Witness the Future
Sorcery
Target player shuffles up to four target cards from their graveyard into their library. You look at the top four cards of your library, then put one of those cards into your hand and the rest on the bottom of your library in a random order.
Anato Finnstark
Rulings
If you choose zero target cards or the cards are illegal targets as Witness the Future resolves, the target player will still shuffle their library.
(wotc • 2021-11-19)
If the player is an illegal target as Witness the Future resolves, the library won't be shuffled and any targeted cards remain in the graveyard.
(wotc • 2021-11-19)
Rulings
If you choose zero target cards or the cards are illegal targets as Witness the Future resolves, the target player will still shuffle their library.
(wotc • 2021-11-19)
If the player is an illegal target as Witness the Future resolves, the library won't be shuffled and any targeted cards remain in the graveyard.
(wotc • 2021-11-19)