Sleep is a magic spell in Final Fantasy VII Rebirth. It is provided by 
Binding Materia, and inflicts the 
Sleep effect, which prevents a target from acting for its duration unless it is awoken earlier.
Use[]
Sleep has a 5 MP cost, and can be used by party members with a level 1 binding materia. It applies the Sleep status effect, which causes a target to be unable to act for its duration, unless it is awoken earlier by a physical attack. This means that the spell can be used to remove a threat temporarily from battle.
Most often, the best use case of Sleep is to temporarily disable a threat so as to focus on others (doing so can also prevent the other AI-controlled party members from attacking it). This is because an enemy under the sleep status will be awoken if attacked physically, vulnerable only to magic damage, and as such it is better to use Sleep merely as a way to avoid them rather than trying to defeat them when they are under sleep. Many higher-level bosses are not actually immune to Sleep.
The Sleep spell can be improved by pairing binding materia with 
Magnify Materia to cast Sleep on all enemies at once, though this may be a less efficient use than pairing it with Time Materia to simply cast 
Stop on all instead. Sleep's duration can be extended with Magic Focus Materia, but this is an inefficient use of the materia.