Sunblade Samurai
Enchantment Creature — Human Samurai
Vigilance (Attacking doesn't cause this creature to tap.)
Channel — 
, Discard this card: Search your library for a basic Plains card, reveal it, put it into your hand, then shuffle. You gain 2 life.
Aaron Miller
Rulings
Discarding the card is part of the cost to activate a channel ability.
(wotc • 2022-02-18)
If a channel ability requires a target, you may not activate it without a target just to discard the card.
(wotc • 2022-02-18)
Rulings
Discarding the card is part of the cost to activate a channel ability.
(wotc • 2022-02-18)
If a channel ability requires a target, you may not activate it without a target just to discard the card.
(wotc • 2022-02-18)