Expelliarmus

You snap your fingers and attempt to disarm a creature in the process of making an attack. The targeted Creature must make a Strength Saving Throw. On a Failed Save, the weapon flies out of their hand, moving 15' away from them, in the direction of the creature they were attacking. If they roll a natural 1, their weapon flies into your hand instead.

You can cast this Spell as a Reaction which you take when you see a creature within 50' of you making an Attack against you, or an ally within 10' of you. You can only use this as a reaction once per round.