Debilitating Smite

The next time you hit a creature with a weapon attack before this spell ends, the weapon gleams with natural radiance as you strike. The attack deals an extra 2d6 necrotic damage to the target. A creature affected by this spell must make a Constitution saving throw against your spell save DC. On a failure, the creature becomes paralyzed until the end of your next turn. On a success, the creature is not paralysed but takes the necrotic damage. 

At Higher Levels. When you cast this spell using a spell slot of 4rd level or higher, the extra damage increases by 1d6 for each slot level above 3st.