Ember's Sapping Shots

You touch a weapon of your choice for the entire casting duration, infusing it with an ability to leech the energy from those the weapon harms. Until the spell ends, every attack made with that weapon deals an additional 1d6 necrotic damage, and after dealing this damage, the creature holding that weapon can spend a reaction to regain hit points equal to your spellcasting ability modifier. 

At Higher Levels: When you cast this spell with a slot of 4th level or higher, the necrotic damage increases by 1d6 for every 2 levels above 2nd level.