Sunbird's Invocation is a rare Enchantment card from Ixalan Promos (PXLN), collector number 165p. Current market price: $0.71 (foil $3.58), TCGplayer market prices via Scryfall.
Whenever you cast a spell from your hand, reveal the top X cards of your library, where X is that spell's mana value. You may cast a spell with mana value X or less from among cards revealed this way without paying its mana cost. Put the rest on the bottom of your library in a random order.