An-Nur 24:28 فان لم تجدوا فيها احدا فلا تدخلوها حتى يوذن لكم وان قيل لكم ارجعوا فارجعوا هو ازكى لكم والله بما تعملون عليم ٢٨

Seeking Permission and the Etiquette of entering Houses

This is the Islamic etiquette. Allah taught these manners (of seeking permission) to His believing servants and commanded them not to enter houses other than their own until they had asked permission, i.e., to ask for permission before entering