Sahih Al Bukhari – Book of Beginning Of Creation

Volumn 004, Book 054, Hadith Number 500.
—————————————–
Narated By Jabir : The Prophet said, "When nightfalls, then keep your children close to you, for the devil spread out then. An hour later you can let them free; and close the gates of your house (at night), and mention Allah's Name thereupon, and cover your utensils, and mention Allah's Name thereupon, (and if you don't have something to cover your utensil) you may put across it something (e.g. a piece of wood etc.)."

in my opinion, here devil has several meanings… as you know that a lot of crimes happen at night time for example, theft, frauds, rapes, illegal meetings etc. so the hadith recommends to keep your childern in house to keep them away from illegal acts. and Allah knows the Best.