Explosive Smite (5e Feat)
From D&D Wiki
Prerequisites: The Divine Smite feature or the ability to cast a smite spell
When you smite your enemies, divine retribution spreads to nearby foes. When you deal damage to a creature with the Divine Smite feature, the Improved Divine Smite feature, or a smite spell, you may choose for it to deal half damage. If you do, you may choose any number of creatures you can sense within 5 feet of your original target. They take the same amount and type of damage.