Sleep is essential for muscle hypertrophy.
While somewhat dated, there was a study in Ergonomics which showed that successive nights of sleep deprivation lowered the performance of athletes for standard lifts (bench press, leg press, deadlift). A more recent meta analysis also showed some data that showed that compound lifts were inhibited by sleep.
On the flipside, exercise does help sleep! Another study showed that in older adults weight training helped with getting to and staying asleep.
While a lot of emphasis is placed on diet with bodybuilding, never forget the importance of a great night's rest.