Leyline of Sanctity is a rare Enchantment card from Modern Masters 2015 (MM2), collector number 23. Current market price: $0.48 (foil $3.26), TCGplayer market prices via Scryfall.
If this card is in your opening hand, you may begin the game with it on the battlefield. You have hexproof. (You can't be the target of spells or abilities your opponents control.)