Throw from the Saddle is a common Sorcery card from Outlaws of Thunder Junction (OTJ), collector number 185. Current market price: $0.17 (foil $0.28), TCGplayer market prices via Scryfall.
Target creature you control gets +1/+1 until end of turn. Put a +1/+1 counter on it instead if it's a Mount. Then it deals damage equal to its power to target creature you don't control.