Joust is a uncommon Sorcery card from Throne of Eldraine (ELD), collector number 129. Current market price: $0.07 (foil $0.31), TCGplayer market prices via Scryfall.
Choose target creature you control and target creature you don't control. The creature you control gets +2/+1 until end of turn if it's a Knight. Then those creatures fight each other. (Each deals damage equal to its power to the other.)