An-Nur 24:27 يا ايها الذين امنوا لا تدخلوا بيوتا غير بيوتكم حتى تستانسوا وتسلموا على اهلها ذالكم خير لكم لعلكم تذكرون ٢٧

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