Devouring Smite

The touch of your light-wreathed weapon can siphon life force from others to heal your wounds. Make a melee attack against a creature within your reach. On a hit, the target takes 3d8 radiant damage, and if the creature dies, you regain hit points equal to half the amount of radiant damage dealt. 

At Higher Levels. When you cast this spell using a spell slot of 4th level or higher, the damage increases by 1d8 for each slot level above 3rd.