Crackling Smite

The next time you hit a creature with a melee weapon attack before this spell ends, the weapon crackles with lightning as you strike. The attack deals an extra 4d6 lightning damage to the target. Additionally, the target must succeed on a Constitution saving throw or be paralyzed until the end of its next turn. 

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