The Prophet (ﷺ) said: When one has a look into the house, then there is no (need of) permission.
Sunan Abi Dawud Book 43, Hadith 401
← Previous Hadith The Prophet (ﷺ) said: If anyone peeps into the house of a people without their permission and he knocks out his eye, no responsibility is incurred for his eye.

Sunan Abi Dawud Book 43, Hadith 400 Next Hadith → A man came. Uthman's version has: Sa'd ibn AbuWaqqas came. He stood at the door. Uthman's version has: (He stood) facing the door. The Prophet (ﷺ) said to him: Away from it, (stand) this side or that side. Asking permission is meant to escape from the look of an eye.

Sunan Abi Dawud Book 43, Hadith 402