This seems like a terrible idea. The whole point of cantrips is that they can be cast whenever you want; after all, there's a massive list of other spells that have x/rest restrictions. If you really really want to make it require a rest, just make it a level 1 spell and buff it accordingly (it's far too weak to justify the restriction right now.)
It utterly guts Arcane Tricksters in particular, who are designed and balanced around being able to cast it whenever they want.
