Thunderous Smite

Source: Player's Handbook

Level 1 Evocation (Paladin)

Casting Time: Bonus Action, which you take immediately after hitting a target with a Melee weapon or an Unarmed Strike
Range: Self
Components: V
Duration: Instantaneous

Your strike rings with thunder that is audible within 300 feet of you, and the target takes an extra 2d6 Thunder damage from the attack. Additionally, if the target is a creature, it must succeed on a Strength saving throw or be pushed 10 feet away from you and have the Prone condition.

Using a Higher-Level Spell Slot. The damage increases by 1d6 for each spell slot level above 1.