The Double-Bladed Scimitar can be found in Eberron: Rising from the Last War, page 21.
When you hit with an attack using this magic sword, the target takes an extra 1d6 cold damage. In addition, while you hold the sword, you have resistance to fire damage.
In freezing temperatures, the blade sheds bright light in a 10-foot radius and dim light for an additional 10 feet.
When you draw this weapon, you can extinguish all nonmagical flames within 30 feet of you. This property can be used no more than once per hour.
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.