25 cards where the text includes “discard a card:” and the colors is W and (the card is available on Paper)

Avenger en-Dal (Nemesis #2)
Aven Trooper (Torment #2)
Charm Peddler (Mercadian Masques #6)
Chivalric Alliance (March of the Machine Commander #11)
Cho-Arrim Alchemist (Mercadian Masques #8)
Devout Witness (Mercadian Masques #17)
Fleeting Spirit (Innistrad: Crimson Vow #14)
Ghost Tactician (Planar Chaos #6)
Goldmeadow Lookout (Future Sight #22)
Guardian of New Benalia (Dominaria United #19)
Hypochondria (Torment #7)
Icatian Crier (Ultimate Masters #22)
Netter en-Dal (Nemesis #13)
Patrol Hound (Odyssey #38)
Peace of Mind (Eldritch Moon #36)
Pegasus Refuge (Tempest #35)
Plargg, Dean of Chaos // Augusta, Dean of Order (Strixhaven: School of Mages #155)
Plargg, Dean of Chaos // Augusta, Dean of Order (Strixhaven: School of Mages #155)
Resilient Wanderer (Odyssey #43)
Seasoned Hallowblade (Core Set 2021 #34)
Stern Constable (Shadows over Innistrad #39)
Thraben Standard Bearer (Eldritch Moon #48)
Tireless Tribe (Odyssey #56)
Tonic Peddler (Mercadian Masques #54)
Trained Pronghorn (Judgment #30)
Vikya, Scorching Stalwart (Universes Within #11)

The message was clear to Sorin—time to search for something else.