Musnad Ishaq

Benefits:
Entering someone’s house without permission is a very grave offense. Whenever you go, you must seek permission. As Sayyiduna Abu Hurairah radi Allahu anhu narrates that he heard the Messenger of Allah sallallahu alayhi wa sallam say: “Whoever peeks into someone’s house without their permission, and they gouge out his eye, then there is no liability (no retribution) for it.” (Muslim, Kitab al-Adab, No. 2158)

However, if someone is sent to call a person, then there is no further need for permission to enter. The act of calling itself is considered granting permission. The one who calls is responsible to make all necessary arrangements for privacy, such as veils and coverings, beforehand, so that the one who is called does not inadvertently see anything inappropriate.