When someone enters his house without saying “Bismillah”, Satan says he has found a place to spend the night
Sahih Muslim 5006
Full Hadith
وعن جابر، رضى الله عنه قال: سمعت رسول الله صلى الله عليه وسلم يقول: “إذا دخل الرجل بيته، فذكر الله تعالى عند دخوله وعند طعامه، قال الشيطان لأصحابه: لا مبيت لكم ولا عشاء، وإذا دخل ، فلم يذكر الله تعالى عند دخوله، قال الشيطان: أدركتم المبيت؛ وإذا لم يذكر الله تعالى عند طعامه قال: أدركتم المبيت والعشاء“))
Jabir bin ‘Abdullah reported Allah’s Messenger (ﷺ) saying:
“When a person enters his house and mentions the name of Allah at the time of entering it and while eating the food, Satan says (addressing himself: You have no place to spend the night and no evening meal; but when he enters without mentioning the name of Allah, the Satan says: You have found a place to spend the night, and when he does not mention the name of Allah while eating food, he (the Satan) says: You have found a place to spend the night and evening meal.”
Lesson
We should enter the house saying Bismillah (In the name of Allah). Who wants Shaitaan to stay in their house? There are many blessings and virtues of saying Bismillah, one of them being that Shaitaan hates those words, thus avoiding any place where these words are said.