The description of Luck Blade (DMG p179) says:
Luck. If the sword is on your person, you can call on its luck (no action required) to reroll one Attack roll, ability check, or saving throw you dislike. You must use the second roll. This property can’t be used again until the next dawn.
Do you have to be attuned to it to receive the benefit, or as the description says, is having it on your person enough?