The Double-Bladed Scimitar can be found in Eberron: Rising from the Last War, page 21.
Bound into this weapon is a level 6 spell. The spell is determined when the weapon is created and must belong to the Conjuration, Divination, Evocation, Necromancy, or Transmutation school of magic. The weapon has 6 charges and regains 1d6 expended charges daily at dawn. While holding the weapon, you can expend 1 charge to cast its spell.
The spell's saving throw DC is 17, and its attack bonus is 9.
If you attack with a double-bladed scimitar as part of the Attack action on your turn, you can use a bonus action immediately after to make a melee attack with it. This attack deals 1d4 slashing damage on a hit, instead of 2d4.
This weapon requires two hands to use. This property is relevant only when you attack with the weapon, not when you simply hold it.