Is the custom of not leaving clothes hanging outdoors at sunset an Islamic custom or a popular tradition?

The Sunnah, as night approaches, is to prevent children and livestock from going out, to close doors, and to mention the name of Allah over them. This is because the devils spread out at this time, and they cannot open a closed door over which the name of Allah has been mentioned. The intent is that mentioning the name of Allah Almighty when closing doors and similar actions is a means of protection from the harm of Shaytan. As for preventing the hanging of laundry to dry at that time, there is no basis for it.