He works the night.
He works at night.
What's the difference?
The main difference is that the first one is not grammatically correct.
If he works every night, then we can say "He works nights" or "He works at night". If it's an occasional event, use "Sometimes, he works at night", "Sometimes, he works all night", "Sometimes, he works during the night" or "Sometimes, he works at night".
If he works somewhere where some people work during the day and some at night, you could use "He works the night shift".